SPM Chemistry Revision Module on the Basics

SPM CHEMISTR Y

R EVISIO N MODULE FOR THE MASTERY OF THE BASICS I N N SPM CHEMISTR Y

Panel : 1. 2. 3. 4.

June Ling S J Chen Soo Chien Felix Ngui Jong Kah Yin

SMK St Joseph, K uching K ole j DPAH A bdilah, K uching SMK Tabuan SMK Tabuan Jaya, K uching SM Sains K uching

Com piled and edited by : Jong Kah Yin

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REVISION MODULE FOR THE MASTERY OF THE BASICS IN SPM CHE CHEM MISTR Y

SPM CHEMISTR Y

I NDE NDEX CONTENT 1

2

R EVISIO N CHECK-LI K-LIST Form 4

4 - 10

Form 5

11 - 15

WRITING EQUATI UATIO NS 2.1 2.2 2.3 2.4 2.5 2.6

3

R e lative Masses particles Mole and Number of p of Gases Mole and Mass & Volume of G Em pir ical and Molecula r F r For mulae Ca lculations involving Acids and Alkali Ther mochemistry stry

Che mical Bond – I – Ionic bond Che mical Bond – C – Covalent bond Pr e par a tion of Salt – Insoluble salt Pr e par a tion of Salt – Soluble salt Rate of R of R ea ea ction Heat of C of Com bustion

23 24 24 – 25 26 27 – 29 29 - 30

32 33 34 35 36 – 37 38 – 39

WR ITTE TTE N PR ACTICAL PAPER - PAPER 3 5.1 Structure Questions 5.2 Essay Que stions

6

17 17 18 – 19 20 20 21

GUIDED ESSAY WRITING FOR PAPER 2 4.1 4.2 4.3 4.4 4.5 4.6

5

Charges of ions For mulae of com pound s R ea of Acid ea ctions of Acid Displacement of Metals ea ction Double de com posit sition r ea Other s

CALC ALCULATI ULATIO NS 3.1 3.2 3.3 3.4 3.5 3.6

4

PAGE

41 – 47 48

SUGGESTED ANSWER S 6.1 Guided Essay for Paper 2 6.2 Wr itten Pr actical Paper – – Paper 3

REVISION MODULE FOR THE MASTERY OF THE BASICS IN SPM CHE CHEM MISTR Y

50 – 57 58 - 64

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STUDENTS’ REVISION CHECKLIST FOR SPM CHEMISTRY

By : JONG KAH YI N N SM SAI N NS K UCHI N NG

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Chapter 2: The Structure of the A tom A. Knowledge (Definition, meaning and f acts) 1)

State the k inetic theory of ma tter . State one exam ple to support the k ine tic theory of matter

2)

What are atom, molecule and ion?

3)

What is melting point?

4)

Def ine proton number and nucleon num ber .

5)

State the mea ning of isotope s.

6)

State the uses of isotopes such as carbon-14 and cobalt-60.

Check

B. Understanding / Application / Analysis 7)

Ex plain why the temperature r emains unchanged dur ing the melting pr ocess .

8)

Ex plain why the temperature r emains unchanged dur ing the f r ee zing pr oce ss .

9)

A solid compound is heated until it converts into gas. Ex plain the changes in ener gy content, f or ce s of attr action between the particles , and arrangement of particles.

10) State the subatomic particles of an atom. Compare and contrast the r elative atomic masses and the r e lative charges of t he s ubatomic pa rticles of an atom. 11)

27 13

Al is the s ym bol of aluminium.

(a) Deter mine the number of neutron of aluminium. (b) Draw the ele ctr on arrangement of a luminium.

C. Synthesis (Exper iment)

o

12) Solid Z has a melting point of 65 C. Descr ibe a la bor atory ex per iment to dete r mine the melting point of Z. Your answer should show how the melting point of Z is deter mined. o

13) Compound W has a f r ee zing point of 82 C. De scr ibe a la bor atory ex per iment to deter mine the f r ee zing point of W .

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SPM CHEMISTR Y

Chapter 3: Chemical Formulae and Equations A. Knowledge (Definition, meaning and f acts) 1)

State the mea ning of r elative atomic mass based on carbon-12 scale .

2)

Def ine mole.

3)

State the mea ning of molar mass

4)

State the mea ning of molar volume of gas.

5)

State the mea ning of em pir ica l f or mula.

6)

State the mea ning of molecula r f or mula.

Check


Ex plain why we could not deter mine the em pir ical f or mula of copper(II) oxide by hea ting copper powder in a cr uc ible.

8)

Compare and contrast em pir ica l f or mula with molecular f or mula us ing ethane as a n exa m ple.

9)

Vinegar is a dilute ethanoic acid with a molecular f or mula of CH3COOH. (a) Find the em pir ica l f or mula of ethanoic acid. (b) Find the percentage com position by mass of carbon in ethanoic a cid.

10) 3.6 g of carbon reacted with 0.8 g of hydrogen to f or m a com pound. (a) Deter mine the em pir ica l f or mula of the compound f or med. (b) Given that the r elative mole cular mass of the compound is 88 g, f ind its molecular f or mula. [R elative atomic mass: C ,12; H, 1] 11) Hydrogen gas is reacted with 20 g of hot copper(II) oxide powder to produce s olid copper and water . (a) Wr ite the chemical equation for the r ea ction. (b) Calculate the maximum mass of solid copper f or med. [R elative atomic mass: Cu, 64; O,16; H ,1]

C. Synthesis (Exper iment) 12) Des cr ibe a la bor atory ex per iment to deter mine the em pir ical f or mula of magne sium oxide. Your answer should include all the pr ecautions and calculations involved. [R ela tive a tomic mass: Mg, 24; O,16]

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SPM CHEMISTR Y

Chapter 4: Periodic Table of Ele ments A. Knowledge (Definition, meaning and f acts) 1)

State the basic pr inc iple of arr anging the elements in the Per iodic Ta ble f r om its pr oton num ber .

2)

State the physical pr operties of Group 1.

3)

State the physical pr operties of Group 17.

4)

State the changes in the atomic s ize and ele ctr one gativity of elements across Per iod 3.

Check

5) State three s pecial pr ope rties of tr ansition elements? B. Understanding / Application / Ana lysis 39 20

X in Per iodic Ta ble. Ex pla in your answer .

6)

State the position of element

7)

When going across Per iod 3 f r om sodium to argon, the atomic size decreases. Ex plain.

8)

When going across Per iod 3 f r om sodium to argon, the electr onegativity incr ea ses. Ex plain.

9)

The r ea ctivity of Group 1 incr ea ses when going down the group. Ex plain.

10) The r ea ctivity of Group 17 decreases when going down the group. Ex plain. 11) Why helium gas is not r ea ctive? 12) X is an element f r om Group 1. X is burnt in oxygen and the product is diss olved in water . What is the property of the solution f or med? Ex plain. 13) Chlor ine gas is diss olved in water . What can you observe if a piece of blue litmus paper is immer sed into the solution f or med? Ex plain. 14) W is an element f ro m Group 1. Pr edict the chemical r ea ction of W with: a) water , b) Oxygen, State the observation and wr ite the chemical equation involve.

C. Synthesis (Ex pe r iment) 15) Des cr ibe a la bor atory ex per iment to compare the r ea ctivity of elements in Group 1: lithium, sodium and potass ium. 16) Des cr ibe a la bor atory ex per iment to compare the r ea ctivity of chlor ine, br omine and iodine in the r ea ction with ir on wool. State the observation and wr ite the chemical equations involve in r ea ctions.

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Chapter 5: Chemical Bond s A. Knowledge (Definition, meaning and f acts) 1)

What is anion?

2)

What is cation?

3)

State two physical pr operties of ionic com pounds.

4)

State two physical pr operties of covalent com pounds .

Check

B. Understanding / Application / Ana lysis 5) Ex plain why sodium chlor ide can conduct electr icity in aqueous state but cannot conduct electr icity in solid state. 6)

Ma gnesium chlor ide and hydrogen chlor ide are two compounds of chlor ine . At r oom condition, magnesium chlor ide exis ts as a solid but hydrogen chlor ide exis ts as a gas. Ex plain why.

7)

Descr ibe the f or mation of ionic bond in s odium chlor ide , NaCl.

8)

By using exam ple, descr ibe the f or mation of cova lent bond between element f ro m Gr oup 14 and eleme nt f r om Group 17.

C. Synth esis 9) Draw electr on arrangement of the compound f or med f r om the f ollowing elements. a) Nitr ogen and hydr ogen, b) Carbon and oxygen, c) Magnesium and chlor ine, d) Carbon and hydr ogen, e) Hydrogen and chlor ine, f) Sodium and oxygen.

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Chapter 6: Electr oc ochemistr y acts) A. Knowledge (Definition, meaning and f ac 1)

State the mea ning of electr olyte.

2)

State the mea ning of electr olys is.

3)

State three f actor s aff ecting electr olysis of an of an aqueous s olution.

Check

B. Understanding / Application / Analysis alysis 4)

Ex plain why solution of hydrogen of hydrogen chlor ide in water can conduct e lectr icity but solution of hydrogen chlor ide in methy b lbenzene cannot conduct electr icity.

5)

By using exam ple, ex plain how the f ollowing f actor s can deter mine the selective dischar ge of ions at the electr od odes. a) Types of e lectr od odes , b) Conce ntr ation of the of the ions.

6)

Descr b ibe the electr olysis of molten lea d(II) br omide.

7)

Descr b ibe the extr action of aluminium by e lectr olys is .

8)

Draw the structure of Daniell cell and ex plain how it can produce electr icity.

9)

Draw the structure of a of a dry cell and ex plain how it can produce electr icity.

C. Synthesis 10) Des cr b ro m lea d(II) oxide by using electr olysis . ibe a la bor atory ex per iment to extract lea d f r 11) Descr b ibe a la bor a tory ex per iment to show that types of electr od odes aff ect the s elective dischar ge of ions in ele ctr olysis of copper(II) su ph lphate solution. 12) You are given magnesium r bbon, ibbon, coppe r p late, magnes ium nitr ate solution, copper(II) 3 su ph lphate solution, conne cting wir es with cr ocod ocodile cli p ps, 250 cm beaker, voltmeter and porous po t. Construct a voltaic cell by using the above mater ia ls. Ex plain how the voltaic cell can produce electr icity. Your answer must include observation and ha lf e quations for r ea ea ction at anode and ca thode. 13) Des cr b ibe a la bor atory ex per iment to construct the ele ctr ochemica l se r ies of magnesium, copper, zinc and lea d.

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Chapter 7: Acids and Bases and Chapter 8: Sal S alts acts) A. Knowledge (Definition, meaning and f ac 1)

State the mea ning of acid and alk ali.

2)

What is the mea ning of strong of strong acid and weak alk ali?

3)

What is ne utr alisa tion?

4)

What is s alt?

5)

What is double decom position r ea ea ction?

Check


The pH va lue of s olution ammonia in water is 9 but the pH v a lue of solution of ammonia in tr ichlomethane is 7. Ex pla in why the pH value s of the of the two s olutions are diff er ent.

7)

80 cm of distilled water is added to 20 cm of 2.0 of 2.0 mol dm of the of the dilute solution.

8)

In a titr ation, 40 cm of 0.25 of 0.25 mol dm potass ium hydr oxide, KOH solution is needed to 3 of the nitr ic acid, HNO3. ne utr alise 20 cm of nitr ic acid, HNO 3. Calcula te the mola r ity of the

9)

Given dilute nitr ic acid and dilute su phu lphur ic acid have the same conc oncentr ation of -3 3 0.5 mol dm . In a neutr alisation ex per iment, 20 cm of nitr ic acid is r equir ed to neutr alise 3 3 20 cm of sodium hydr oxide solution but only 10 cm of su phu lphur ic acid is r e quir ed to 3 ne utr alise 20 cm of sodium hydr oxide solution. Ex plain why.

3

3

3

-3

s olution of HC HCl. Find the molar ity

-3

C. S ynthesis 10) Des cr b ibe a chemical test to show that a give n solution is an acid. 11) Des cr b ibe a la bor atory ex per iment to deter mine the conce ntr ation of sodium hydr oxide by -3 us ing titr a tion process. You are given 0.2 moldm of dilute su phu lphur ic acid, ph d, pheno ph lphthale in, burette, p p ipette and conical f lask . 12) You are given s olid sodium chlor ide. Descr b ibe how you can prepare sodium chlor ide -3 3 solution of 0.2 of 0.2 mol dm in la bor atory by using 250 cm volumetr ic f lask . 13) Des cr b ibe the pr e par ation of zinc su ph lphate . 14) Des cr b ibe the pr e par ation of lea d(II) chlor ide. 15) Des cr b ibe the pr e par ation of po potass ium nitr ate. 16) Solid W is a salt. Descr b ibe the tests you would carry out to conf ir m the presence of zinc ions and nitr ate ions in the sa lt 17) Solid X is a metal carbonate. Beside hea ting, de scr b ibe che mical tests that you would carry out to conf ir m that X consists of carbonate ions. . 18) You are give n f ou illed with solution consisting zinc ions, lea d(II) ions, aluminium our test tubes f ill ions and magnesium ions r es pectively. Descr b ibe the tests you would carry out to conf ir m the ion that is present in each test tube. 19) You are given pota ss ium chlor ide solution, lea d(II) oxide powder and dilute nitr ic acid. Descr b r om the given mater ials. ibe how you would prepare lea d(II) chlor ide sa lt f r 20) You are given dilute su phu lphur ic acid, copper(II) nitr a te solution and sodium car bonate solution. De scr b r om the give n mater ials . ibe how you would prepare coppe r(II) su ph lphate salt f r

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Chapter 9: Manufactured Substance in Industr y acts) A. Knowledge (Definition, meaning and f ac 1)

What is the mea ning of alloy? State the aims of mak ing alloys .

2)

What is the mea ning of com pos ite mater ials? State the components of the of the f ollowing com posite mate r ials: a) R einf or ced conc oncr ete, b) Super conduc onductor , c) F b ibr e optic, d) F b ibr e glass , e) Photochr omic glass .

3)

State the ca talyst, temperature and pressure of the of the f ollowing p ng pr oc ocess : a) Contact pr ocess b) Haber pr ocess

4)

What is the mea ning of po polymer s? Name the monomer of monomer of po polythe ne and polyvinyl chlor ide.

5)

State f ou of each gla ss . our types of glass and the ir com positions . List the uses of each

6)

What is ce r amics? State the pr op operties and list the uses of cer amics.

Check


Bronze is an alloy consis ting of copper and tin. Ex plain why bronze is harder than coppe r .

8)

Ex plain how acid r ain is f or me d. Descr b ibe how a cid r ain causes envir on onmental pollution.

9)

Ex plain the industr ial process involve d in the ma nuf a ctur e of su phu lphur ic acid. Wr ite all the chemical equations involve d.

10) Ex plain the industr ial process involved in the manuf actur e of ammonia gas. Wr ite all the chemical equations involve d.

C. S ynthesis 11) Des cr b ibe a la bor atory ex per iment to prepare ammonium su ph lphate (a mmonium f ertiliser) brass and copper . 12) Des cr b ibe a la bor atory ex per iment to compare the hardness of brass

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Chapter 10: Rate of R eaction A. Knowledge (Definition, meaning and f acts) 1)

What is rate of r ea ction?

2)

What is stated in the collision theory?

3)

What is activation ener gy?

4)

What is eff ective collis ion?

Check


Ex plain how total sur f ace area (size of reactant) can incr ea se the rate of r ea ction based on collision theory.

6)

Based on collis ion theory, ex plain how temperature can incr ea se the rate of r ea ction.

7)

Based on collis ion theory, ex plain how catalyst can incr ea se the rate of r ea ction.

8)

Ex plain why hydr och lor ic acid of 2.0 mol dm -3 hydr ochlor ic acid of 0.5 mol dm .

-3

is reacted f aster with zinc compare to

C. S ynthesis 9)

Hy pothes is: The smaller the size of solid reactant, the higher the rate of r ea ction. Descr ibe a la bor a tory ex pe r iment to conf ir m the hy pothesis by using the r ea ction betwee n calcium carbonate and hydr ochlor ic acid.

10) Des cr ibe a la bor atory ex per iment to show that the presence of catalyst will incr ea se the rate of decom position of hydrogen per oxide. 11) Des cr ibe a la bor atory ex per iment to show that an incr ea se in temperature will incr ea se the rate of r ea ction between sodium thiosu lpha te solution and su lphur ic acid.

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Chapter 11: Carbon com pounds A. Knowledge (Definition, meaning and f acts) 1)

What is homologous se r ies?

2)

What is saturated hydrocarbon and unsaturated hydrocarbon? State an exam ple of each of them.

3)

What is polymer ? State an e xam ple of polymer and its monomer .

4)

What are saturated and unsaturated f ats?

Check


Ex plain what is isomer s and isomer ism by using butane as an exam ple.

6)

Ex plain why ethene gas can decolour ise s the acidif ied potass ium ma ngante(II) solution whereas ethane cannot decolour is es acidif ied pota ss ium mangante (II) s olution.

7)

Ex plain why both hexane and hexane having s ix carbon atoms per molecule but hexene burns w ith a more sooty f lame than hexane

8)

Pentane and propane are members f r om the alk ane f amily. Ex plain why the melting point of pentane is higher than pr opane.

9)

Pr opa nol and pr opanoic acid are diss olve d in water. It is f ound that pr opanol solution is a ne utr al but pr opanoic acid is an acidic s olution.

10) Ex plain the coagula tion process of latex. 11) Ex plain how to prevent coagulation of latex.

C. S ynthesis 12) Des cr ibe a test to diff er ential hexene and hexane. 13) Des cr ibe a la bor atory ex per iment to prepare ethane gas f r om e thanol. 14) Des cr ibe a la bor atory ex per iment to prepare ethanoic acid f r om etha nol. 15) Ethyl propanoa te is a product f ro m r ea ction between a lcohol and car boxylic acid. (a) State two physical pr operties of ethyl pr opa noa te. (b) Descr ibe a la bor atory ex per iment to prepare ethyl pr opanoate. Your answer must include a diagr am of the apparatus set-up and the che mical equation involved. 16) Ex plain how to prepare pr opanoic acid f r om pr opene.

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Chapter 12: Oxidation and R eduction A. Knowledge (Definition, meaning and f acts)

Check

1)

What is oxidation and r eduction based on loss or ga in of oxygen?

2)

What is oxidation and r eduction based on tr ansf er of electr ons?

3)

What is oxidation and r eduction based on changes in oxidation num ber ?

4)

What are redox r ea ctions? State an exam ple of redox r ea ctions .

5)

What is oxidising agent and r educing agent? State an exa m ple of oxidis ing agent and r educing agent.


Deter mine whether the r ea ction between hydr och lor ic acid and s odium hydr oxide is a r edox r ea ction. Ex pla in your answer based on changes in oxida tion num ber .

7)

Deter mine whether the r ea ction between lea d(II) nitr ate and copper(II) is a redox r ea ction. Ex plain your answer based on changes in oxidation num ber .

8)

The r ea ction between z inc and copper(II) su lphate solution is a redox r ea ction. Ex plain.

9)

When br omine water is added to the potass ium iodide solution, the solution changes colour f r om colour less to brown. Ex plain the observa tion.

10) Des cr ibe the r usting of ir on. 11) A mixtur e of copper(II) oxide and aluminium powder is heated str ongly. The mixtur e bur ns br ightly. Ex plain this observation based on oxidation and r eduction. 3

12) Chlor ine water is added to potass ium iodide solution in a test tube. 2 cm of 1,1,1tr ichlor oe thene is added to the test tube and the mixtur e is shaken thor oughly. The colour of 1,1,1-tr ichlor oethe ne changes f r om colour less to pur ple. Ex plain the obs ervation.

C. S ynthesis 13) Des cr ibe a la bor atory ex per iment to change the oxidation number of ir on f ro m +2 to +3. How would you conf ir m that iron(III) is f or med? 14) Des cr ibe a la bor atory ex per iment to change the oxidation number of ir on f ro m +3 to +2 by us ing zinc.

15) Des cr ibe the extr action of ir on. 16) You are given lea d, zinc, copper and their oxides . Descr ibe a la bor atory ex per iment to compare the r ea ctivity of these metals toward oxyge n.

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Chapter 12: Ther mochemistr y A. Knowledge (Definition, meaning and f acts) 1)

What is exother mic r ea ction and endother mic r ea ction? State an exam ple for each r ea ction.

2)

What is heat of pr ec ipitation?

3)

What is heat of dis placement?

4)

What is heat of neutr alis ation?

5)

What is heat of com bustion?

Check


Ex plain how exother mic r ea ction and endother mic are f or med based on energy change dur ing f or mation and br ea k ing of che mical bonds.

7)

Ex plain why the heat of com bustion of buta nol is highe r than ethanol.

8)

Ex plain why the heat of neutr alisation between strong acids and strong alk a lis is a -1 constant, that is -57k Jmol

9)

Ex plain why the heat of neutr alisation between etha noic acid and sodium hydr oxide is less -1 than -57k Jmol -3

3

-3

3

10) 50 cm of 2 moldm sodium hydr oxide solution is added to 50 cm of 2 mol dm o hydr ochlor ic acid. The temperature incr ea ses t C. 3 -3 3 -3 a) If 100 cm of 2 mol dm sodium hydr oxide solution is added to 100 cm of 2 mol dm hydr ochlor ic acid, pr edict the incr ea s e in tem per atur e . 3

-3

3

-3

3

-3

3

-3

b)

If 50 cm of 1 mol dm sodium hydr oxide solution is added to 50 cm of 1 mol dm hydr och lor ic acid, pr edict the incr ea s e in tem per atur e .

c)

If 50 cm of 4 mol dm sodium hydr oxide s olution is added to 50 cm of 4 mol dm hydr ochlor ic acid, pr edict the incr ea s e in tem per atur e .

C. S ynthesis 11) Des cr ibe a la bor atory ex per iment to deter mine the heat of dis placement of copper by zinc. 12) Des cr ibe a la bor atory ex per iment to deter mine the heat of neutr alis ation between str ong acids and strong alk alis . 13) Des cr ibe a la bor atory ex per iment to deter mine the heat of com bus tion of me thanol. 14) The higher the number of carbon atoms per molecule, the higher is the heat of com bus tion Descr ibe a la bor a tory ex pe r iment to prove that the above statement is true by us ing metha nol, ethanol, pr opan-1-ol, butan-1-ol and pentan-1-ol. “

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Chapter 13: Chemicals for Consumer s A. Knowledge (Definition, meaning and f acts) 1)

What is soa p?

2)

What is sa ponif ication pr ocess ?

3)

What is deter gent?

4)

State the f unctions of each of the f ollowing additives in dete r gent. a) Whitening agent(exam ple : s odium pe r bor ate) b) O ptica l whitener(f luor escent dyes ) c) Biological enzyme (Exam ple: amylas es , li pases, proteases and cellulases) d) Fr agr anc e

5)

What is hard water ?

6)

State the f unction of each of the f ollowing f ood additives : a) Pr eserva tives ( Sodium nitr ite, s odium be nzoate ) b) Antioxida nts (As cor bic acid) c) Flavour ings (Monos odium glutamate (MSG), As partame) d) Sta bilis er s e) Thick ener s

7)

State the f unctions of the f ollowing modern medicines . a) Analges ics ( As pir in, Pa r acetamol, Code ine) b) Ant ibiotics ( Penicillin, Str e ptomycin) c) Psychothe r a peutic medicine ( Stimulant, Antide pr ess ant, Ant ipsychotic)

8)

State the s ide eff e cts of par aceta mol and a s pir in.

Check


Descr ibe the clea nsing action of soa p.

10) Ex pla in why the clea ns ing action of a detergent is more eff ective than a soap in hard wate r .

C. S ynthesis 11) De scr ibe a la bor atory ex per ime nt to prepare soap f ro m palm oil using the sa ponif ication pr ocess . 12) De scr ibe a la bor atory ex per ime nt to inves tigate the clea ns ing action of a soap and a detergent in hard wa ter .

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2. WRITING EQUATIO NS 2.1 FORMULAE OF IO NS 2.2 CHEMICAL FORMULAE OF COMPOUNDS 2.3 REACTIO NS OF ACIDS 2.4 DISPLACEME NT OF METALS 2.5 DOUBLE DECOMPOSITIO N REACTIO N 2.6 OTHER S

By : JONG KAH YI N SM SAI NS K UCHI NG

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2.1 Charges of cations and anions Ions

For mula

Ions

Ammonium ion

Nitrate ion

Carbonate ion

Sulphate ion

Sulphide ion

Phosphate ion

Sodium ion

Magnesium ion

Oxide ion

Iron(II) ion

Aluminium ion

Hydroxide ions

Bromide ion

Silver ions

Lead(II) ions

Calcium ion

For mula

2.2 Formulae of com pounds

SUBSTANCE Naphthalene

For mula

Type of com pound

Type of particles

C10H8

Nitric acid Zinc carbonate Silver chloride Magnesium Lead(II) chloride Sulphur trioxide Ammonia gas Sulphuric acid Zinc carbonate Iron(II) sulphate Hydrogen chloride Aluminium sulphate Calcium hydroxide Copper(II) nitrate

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2.3 WRITING CHEMICAL/ IONIC / HALF EQUATIO NS A. Chemical Properties of Acid 2.3.1 Metal + Acid Hydr ogen + Salt Example : Chemical Equation : Fe + 2HCl H2 + FeCl2 Ionic equations : Fe (s) + 2HCl (aq) H2 (g) + FeCl2 (aq) + 2+ Fe + 2H + 2 Cl H2 + Fe + 2 Cl 2+

Half Equations : Fe Fe + 2 H + 2e Applicable in topics : a. Acid & Bases 1. Nitric acid +

+ 2e H2

b. Preparation of Salts

c. Rate of reaction

Lead

Chemical reaction Ionic equation Half equations

2. Hydrochloric acid +

Zinc


3. Sulphuric acid

+

Magnesium


4. Nitric acid + Aluminium Chemical reaction Ionic equation Half equations

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2.3.2 Acid

+

Base

Example : H2SO4 2H NO3 Applicable in topics: a. Acid & Bases

Water + 2KOH + ZnO

+

Salt 2 H2O + H2O +

b. Preparation of salts

K 2SO4 Zn(NO3)2

c. Thermochemistry

5. Hydrochloric acid + Calcium oxide Chemical reaction Ionic equation

6. Nitric acid

+ Barium hydroxide

Chemical reaction Ionic equation

7.

Sulphuric acid + Sodium hydroxide

2.3.3 Acid

Metal Carbonate

+

Water + Carbon dioxide +

Salt

Example : 2HCl + ZnCO3 H2O + CO2 + ZnCl2 Applicable in topics: a. Acid & Bases b. Preparation of salts and qualitative analysis of salt c. Rate of reaction 8. Sulphuric acid

+ Sodium carbonate solution


9. Hydrochloric acid

+

calcium carbonate granules


10. Nitric acid

+

copper(II) carbonate


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SPM CHEMISTR Y

2.4. Displacement of metal r eactions Example : Cu(NO3)2 (aq) + Zn (s) Cu (s) + Zn(NO3)2(aq) Applicable in topics: 1. Electrochemistry 2. Redox 3. Thermochemistry 11. Silver nitrate solution + Iron metal Chemical reaction Ionic equation Half equations

12. Copper(II) sulphate solution + Magnesium metal Chemical reaction Ionic equation Half equations

2.5. Double decom position Example : AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3(aq) Applicable in topics: 1. Salts preparation 2. Thermochemistry 13.

Lead(II) nitrate solution + Potassium chloride solution


14.

Copper(II) nitrate solution + sodium carbonate solution


15.

Barium chloride solution + sulphuric acid


16.

Calcium nitrate solution


+ potassium sulphate solution

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SPM CHEMISTR Y

2.6 Other s 17.

Potassium iodide solution + Bromine water


18.

Magnesium + chlorine gas

Chemical reaction Half equations

19. Complete combustion of ethanol Chemical reaction

20. Complete combustion of propene Chemical equation

21. Heating of zinc nitrate Chemical Equation

22. Heating of copper(II) carbonate Chemical Equation

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3. CALCULATIO NS 3.1

RELATIVE MASSES

3.2

MOLE AND NO. OF PAR TICLES

3.3

MOLE AND MASS & VOLUME OF GASES

3.4

EMPIRICAL AND MOLECULAR FOR MULAE

3.5

CALCULATIONS INVOLVING ACIDS & ALKALI

3.6

THER MOCHEMISTR Y

By : JUNE LING S J SMK ST JOSEPH, K UCHI NG

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3.1 Calculate Relative Molec ular Mass (Mr ) or Relative Formula Mass (Mr ) from Relative Atomic Mass(Ar )

Relative Atomic Mass of an element, Ar = A ver a ge mass of on e atom of an element bon -12 1/12 x mass of one atom of ca r Example 1 : How may times is one calcium atom heavier than one oxygen a tom? [RAM O,16; Ca,40]

Solution: Mass of one Ca atom Mass of one O atom

40 16

=

2.5

The mass of one Ca atom is 2.5 times hea vier than one oxygen atom. Example 2 : How may calcium atoms have the same mass as two atoms of br omine? [RAM Br, 80]

Solution: Mass of two atoms of br omine = 2 x 80 = 160 Number of calcium atoms = 160 = 4 40 Relative Molec ular Mass of a molecule, Mr, =

Average mass of one molec ule 1/12 x mass of one atom of ca r bon -12

For ionic compounds, the term Relative Formula Ma ss, is used in place of relative molec ular mass. Calculate Mr by adding up all the Ar of all the atoms present in the covalent molecule or on e formula unit of the ionic com pound. Ar and Mr have no un its.

Example 1 : Find the RMM and RFM of the following substances : Molecular Subs tances Oxyge n Hydr ochlor ic acid Water Su lphur ic a cid Ammonia

Molecula r For mula O2 HCl H2O H2SO4 NH3

R e lative Molecular Mass (RMM) 2(16) = 32

[Ar : S, 32; O, 16; H, 1; Cl, 35.5; N, 14]

Ionic Com pounds

Che mical R elative For mula Mass (RFM) For mula NaCl 23 + 35.5 = 58.5 Sodium chlor ide Aluminium oxide Al2O3 Calcium car CaCO3 bonate Hydrated Copper(II) Su lphate CuSO4.5H2O [Ar : Na, 23; Cu, 64; Al, 27; Ca, 40; O, 16; H, 1; Cl, 35.5; S, 32]

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SPM CHEMISTR Y 3.2 The Mole and the Number of Par ticles 23

1 mole = 6.02 x 10

number of par ticles.

There are three kinds of par ticles: atoms molec ules ions

Number of particles = n x NA

where n = number of moles 23 NA = Avogadr o s Constant, 6.02 x 10 ’

Exam ple 1 How many zinc atoms are there in 0.5 moles of zinc powder ?

Solution: 23 The number of zinc atoms in 0.5 moles of zinc powder = 0.5 x 6.02 x 10 23 = 3.01x 10 Exam ple 2 (a) How many water molecules are there in a glass containing 3.5 moles of w ater ? (b) How many hydrogen atoms are there in the glass ?

Solution: 23 (a) The number of water molecule s in 3.5 mole s of water = 3.5 x 6.02 x 10 24 = 2.17 x 10 (b) One molecule of water, H2O, contains two hydrogen atoms. 23 The number of hydrogen atoms in 3.5 moles of water = 2 x 3.5 x 6.02 x 10 24 = 2 x 2.17 x 10 24 = 4.21 x 10 Exam ple 3 23 (a) Find the number of moles of oxygen gas, O2, containing 3.01x 10 molecules of oxygen gas.

Solution: Number of pa r tic les = n x N A number of moles of oxygen gas, O2, n = N um ber of par ticle s NA 23

= 3.01x 10 23 6.02 x 10 = 0.5 Exam ple 4 A beaker conta ins 0.2 moles of MgCl2. Find the total number of ions in the bea k er .

Solution: 2+ 1 mole of MgCl2 gives 1mole of Mg and 2 moles of Cl ions i.e. 3 moles of ions in total. Number of moles of ions in 0.2 moles of MgCl2 = 0.2 x 3 = 0.6 23 23 Number of ions = 0.6 X NA = 0.6 x 6.02 x 10 = 3.61 x 10

C) Equa tions for ca lculating the nu m ber of moles, n, in:

a ) Substance s n =

_ m Molar mass

m= mass of a subata nce Molar mass = A r or M r in gr ams

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b) Solutions n = MV

-3

M = mola r ity in mol dm 3 V = v olume of the solution in dm 3

When the volume of the solution is given in cm , n =

MV 1000

V = volume of the s olution in cm

3

c ) G as es n=

Volume of a gas Molar volume

3

volume of a gas in dm 3 3 Molar v olume, Vm = 22.4 dm at STP or 24 dm at room conditions

Note : -1

Molar Ma ss = mass of 1 mole of a substance in gmol = Ar or Mr in gr ams Molar Volume = volume o cc up ied by 1 mole of all g as es 3 3 [i.e. 22.4dm at STP or 24dm at room c ond itions] Review Question 1: Calculating number of moles, mass in substances. Use equ ations in (a) a bove

1. Zinc, Zn Ar = 65 Calculate a) Mass of 1 mole

b) Ma ss of 2 mole s

2. Sodium Hydr oxide, NaOH a) Mass of 3 mole s of NaOH:

d) Mass of 3.01 x 10 atoms

23

Zn

Mr = 23+16+1 = 40 b) Number of mole s in 20g of N aOH:

3. Carbon dioxide gas, CO2 , Mr = a) Mass of 2.5 moles of CO2 gas:

4. Sodium chlor ide, Na Cl a) Mass of 0.65 moles :

c) Mass of ½ moles

b) Number of molecules in 1.5 moles of CO2 gas:

c)

Number of atoms in 2 moles of CO2 ga s:

Mr =

5. Copper(II) nitr ate, Cu(NO3)2 Mr = a) Number of moles in 56.4g of copper(II) nitr a te

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[Ar : Zn, 65; Na, 23; Cu, 64; O, 16; H, 1; C, 12; Cl, 35.5; N, 14]

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Example 2: Calculate the molarity of the solution obtained when 14 g of potass ium hydroxide is 3 completely dissolved in distilled water to make up 500cm of solution. [Ar : K,39 H,1; O,16] Solution: Use equation in (b) a bove. Molar ity of KOH, M = n x 1000 Number of moles of KOH, n = 14 v [39+16+1] = 0.25 x 1000 = 0.25 500 -3 = 0.5 mol dm Example 3 Calculate the volume occ up ied by the following gases at STP. i) 2 moles of carbon dioxide ga s ii) 16g of oxygen gas

Solution: Use equation in (c) a bove. i) Number of moles , n = _ Volume of the gas, V molar volume, Vm Volume occupied by 2 moles of CO2,

V = n x Vm = 2 X 22.4 3 = 44 .8 dm

ii) n = mass of oxygen g a s, O2 Mr of oxygen gas,O2 = 16 32 = 0.5 mol Volume occupied by 16g of O2 gas, v = n x 22.4

= 0.5 x 22.4 3

= 11.4 dm 3.5 Using Empirical Formula to find Molec ular For mula

Em pir ica l For mula is the s im plest whole number ratio of number of atoms of each element in the c om pound. Molec ular For mula shows the ac tual number of atoms of each element present in a molecule of the c om pound. Molec ular Formula = (Empirical For mula )n

% composition by mass of an element in a compound = Total mass of the element in the com pound Mr of the com pound Example 1: When 100grams of a hydrocarbon gas i s analys ed, it i s found to contain 85.72% bon and 14.28% hydr og en. ca r

Element Per ce ntage composition by mass /% Per 100 g Number of moles of atoms Mole r a tios Simplest mole r atios

C 85.72

85.72 85.72 = 7.14 12 7.14 = 1 7.14 1

H 14.28

14.28 14.28 = 14.28 1 14.28 = 2 7.14 2

Question gives % by mass instea d of the mass of ea ch elements in the com pound. Per 100 g Divide the mass of each element by its molar mass Divide each number by the smalles t num ber Get the sim plest whole num ber r atio

6 2 e

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Em pir ica l For mula = CH2

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Example 2: 2.58g of a hydrocarbon cont ains 2.16g of carbon. The relative molecular mass of the hydrocarbon is 86. [Ar : H,1; C,12 ] Find the empirical formula and determine the molecular formula of the hydr oca r bon.

Solution: Step 1: Find the Em pir ical For mula by using the ta ble below. Element Mass of e lement/g

C

Number of moles of atoms Mole r a tios

Simplest mole r atios

H

2.16

0.42

2.16 = 0.18 12 0.18 = 1 0.18

0.42 = 0.42 1 0.42 = 2.33 = 7 0.18 3

Wr ite down the mass of the elements as given by the question Divide the mass of each element by its molar mass Divide each number by the sma llest num ber

3

7

Get the sim plest whole number r atio

Em pir ica l For mula = C3H7 Step 2: Find the molecular f or mula of the hydr ocar bon Molecular For mula = (Em pir ical For mula)n = (C3H7)n

Mr = (Sum of the Ar of all atoms in the Em pir ical For mula) x n 86 n

= [ 3(12) + 7(1)] x n = 86 = 2 43

Molecular f or mula : (C3H7)2 = C6H14

3.5 Calculations in Acids and alk alis

Concentration can be expressed in two wa ys: -3

Mass of solute in gr am/g 3 Volume of solvent /dm

i) Concentration of a solution (g dm ) = -3

ii) Molarity of a solution (mol dm ) =

M

=

Num ber of moles of solute/mol 3 Volume of solvent / dm

n

V -3 -3 iii)Conversion between Molarity (mol dm ) and con ce ntr ation in (g dm ):

Molar ity

x Molar Ma ss

-3

Concentr ation -3

(mol dm )

(g dm ) ÷ Molar Mass

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Example 1: Calculate:a)the molarity of a solution which is prepared by dissolving 0.5 mole of hydrogen chloride, HCl, 3 in distilled water to make up to 250 cm solution. [Ar : H,1; Cl,35.5 ]

Solution: a)From n = MV 1000 M = n x 1000 V = 0.5 x 1000 250 -3 = 2 mol dm 3

Example 2: Find the mass of sodium hydroxide that shou ld be dissolved in water to produce 500cm 3 of 0.5 moldm sodium hydroxide solution ? [A :H,1; Na,23; O,16]

Solution: Number of moles of NaOH, n = MV 1000 = 0.5 x 500 1000 = 0.25 Mass of 0.25 mole s of NaOH = number of moles x molar ma ss = 0.25 x [23+16+ 1] = 0.25 x 40 = 10g

Neutr alisation Neutr alisa tion is a r ea ction between an acid and a base to f or m s alt and water only. Acid A + alk ali B s alt and water aA + bB pr oducts

Then,

MAVA MBVB

MA = Mola r ity of acid A MB = Molar ity of alk ali B VA = Volume of acid A VB = Volume of alk ali B a = mole r atio of acid A to alk a li B

= a

b

b 3

3

Note: Make sure that VA and VB are in the same units; both in cm or both in dm 3

-3

Exam ple 1: 27.50cm of 0.15 mol dm of the s odium hydr oxide solution.

3

H2SO4 com ple tely neutr alizes 25.0 cm of NaOH. Calculate the molar ity

Solution: Step 1: Wr ite the chemical equa tion for neutr alization: H2SO4 + 2 NaOH

Na2SO4 + 2H2O

Step 2: Lis t down the value s given by the que stion for each letter in the f or mula: MAVA MBVB

= a

b

MA = 0.15 mol dm VA = 27.50 cm a =1 b 2

3

3

MB = ?

3

VB = 25.0cm

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Step 3: Rearrange the f or mula above. Substitute the values into the f or mula to calculate the r equir ed molar ity. Molar ity of NaOH, MB = b a

x MAVA = 2 x 0.15 x 27.50 VB 1 25.0 3 = 0.33 mol dm 3

R e view Question 1: Repeat the above r ea ction by using 0.15 moldm hydr ochlor ic a cid, HCl. Find the volume 3 3 3 of the acid r equir ed to com pletely neutr alize 25.0cm of 0.33 mol dm of NaOH solution. (Ans: 55.00cm ; note that HCl is a monopr otic acid whereas H2SO4 is a d ipr otic acid )

Pr e par ation of a solution by dilution method Moles of solute bef or e dilution = moles of solute af ter dilution

M1V1

=

M1 = mola r ity of the solution bef or e water is added V1 = volume of the s olution bef or e water is added M2 = mola r ity of the solution a f te r water is a dded V2 = volume of the s olution af ter water is added

M2V2

Note: Make sure that V1 and V2 are of the same un it. -3

Exam ple 1: Calcula te the volume of 2.0 mol dm -3 dm of the same acid solution.

3

s u lphur ic a cid, H2SO4, needed to prepare 2.5 dm of 0.5 mol -3

M1 = 2.0 mol dm -3 M2 = 0.5 mol dm

M1V1 = M2V2

V1 = M2V2 = 0.5 x 2.5 = 0.625 dm M1 2.0

3

or 62.5cm

V1 = ? 3 V2 = 2.5 dm

3

R e view que stions: -3 3 3 1. Find the volume of 2.0 mol dm su lphur ic acid, H2SO4, needed to prepare 100 cm 0.5 mol dm s u lphur ic 3 acid. (Ans: 25cm ) 3

-3

3

2. 200 cm of 1.0 mol dm su lphur ic acid, H2SO4, is poured into a 250 cm volumetr ic f las k . Distilled water is 3 then added to make 250 cm of solution. What is the molar ity of the diluted acid solution? -3 (Ans: 0.8 mol dm ) 3.6 Calculations in Ther moche mistr y Ca lculate: heat of pr ec ipitation, ∆H ppt heat of dis placeme nt, ∆Hdisp heat of neutr alization, ∆Hneut (exother mic) heat of com bus tion, ∆Hcomb (exother mic)

Ste p 1: Wr ite the chemical equation for the r ea ction m= total mass of s olution or w ater/g Ste p 2: Calculate H= mcθ -1 0 -1 c = s pecif ic heat ca pacity of water= 4.2J g C 0 θ = temperature change/ C H = heat r elea sed or absorbed in joules. Ste p 3 : Calculate number of moles, n, of the products f or med in dis placement, pr ec ipitation neutr alization r ea ctions and the number of mole s of the reactant burnt in com bustion. Step 4: ∆H =

H n x 1000

-1

Units of ∆H is in KJ mol but units for H is in J Add a negative sign in front of ∆H for exothermic reaction and a positive sign in front of ∆H for endothermic r eac tion.

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3

-3

-3

3

Exam ple 1: When 100cm of 2.0mol dm lea d(II) nitr ate s olution is added to 100 cm of 2.0 mol dm 0 potass ium su lphate solution, the temperature of the mixtur e incr ea ses by 9 C. What is the heat of pr ec ipitation?

Step 1: Wr ite the chemical equation for the pr ec ipitation r ea ction: NO3(aq) PbSO4 (s) + 2K

Pb(NO3)2(aq) + K 2SO4(aq)

3

m = total mass of solution = (100+100) cm -1 0 -1 c = s pecif ic heat ca pacity of water = 4.2J g C 0 0 θ = temperature change/ C = 9 C

Ste p 2: Calculate H= mcθ = 200x4.2x 9 = 7560J

Ste p 3 : Calculate number of moles, n, which is the same for both reacting solutions: n = MV 1000

= 2.0 x 100 = 0.2 1000

Step 4 : ∆H =

H n x 1000

7560 0.2 x 1000 -1 = 37.8 kJ mol

=

Exam ple 2: When 30 g of butane C4H10 is com ple tely burnt in air , the heat energy r e lea sed incr ea s es the 3 0 temperature of 500 cm of water by 70 C. Find the heat of com bus tion of butane.

Ste p 1:Calculate H= mcθ = 500 x 4.2 x 70 J = ? Ste p 2 : Calculate number of moles, n of butane. Mr [C4H10] = 4(12) + 10(1) = 58 Number of moles of butane =

mass Molar mass = ?

Step 3 : ∆H =

H n x 1000

? _? _ x 1000 =

=

-1

kJ mol (Remember to add the negative s ign for e xother mic r ea ction)

-1

(Answer: - 284.33 kJ mol ) 3

-3

3

-3

R e view Question: 50 cm of 1 mol dm nitr ic acid is added to 50 cm of 1 mol dm pota ss ium hydr oxide. The 0 temperature of the mixtur e incr ea ses by 6.5 C. Ca lculate the heat of neutr alization of the solution. -1 ( Ans: - 54.6 kJ mol )

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4. GUIDED ESSAY WRITING FOR PAPER 2 4.1

CHEMICAL BOND – IONIC BO ND

4.2

CHEMICAL BOND – COVALENT BO ND

4.3

PREPAR ATIO N OF SALT – I NSOLUBLE SALT

4.4

PR EPAR ATIO N OF SALT – SOLUBLE SALT

4.5

RATE OF REACTIO N

4.6

HEAT OF COMBUSTIO N

By : CHEN SOO CHIE N KOLEJ DPAH ABDILLAH, K UCHI NG

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4.1 CHEMICAL BONDS: IONIC BO ND Guide d Exe r cise

Exer cis e

1.

2.

Element Proton A B The r ea ction between atoms A and ionic com pound.

num ber 3 9 B f or ms an

Ele ment Proton num ber C 12 D 8 The r ea ction between atoms C and D f or ms an ionic com pound.

(i) Ex plain how this ionic compound is f or med. (ii) Draw the electr on arrangement of the compound f or med.

(i) Ex plain how this ionic compound is f or med. (ii) Draw the electr on arrangement of the compound f or med.

Ans wer :

Answer :

(i) ……….. A has electr on arrangement of …….. To achieve the …………. ele ctr on arrangement // ……….. arrangement, atom A …………. one + valence e lectr on and a …………… ion, A is f or med. → [A ]

………… B has e lectr on arrangement of ……….. To achieve the …………. ele ctr on arrangement // ………… arrangement, atom B ………….. one electr on and a ……………… ion, B is f or med. [B +

→

]

-

A and B ions are attracted to each other by electr ostatic f or ces to f or m an ionic com pound AB. (ii)

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4.2 CHEMICAL BONDS: COVALENT BO ND Guided Exer cise

Exer cise

1.

2.

Element No of pr otons N 7 H 1 The r ea ction between nitr ogen and hydr ogen atoms f or ms a covale nt com pound.

Element No of pr otons C 6 Cl 17 The r ea ction between carbon and chlor ine atoms f or ms a covale nt com pound.

(i) Ex plain how this covalent compound is f or med. (ii) Draw the electr on arrangement of the compound f or med.

(i) Ex plain how this covalent compound is f or med. (ii) Draw the electr on arrangement of the compound f or med.

Ans wer :

Answer :

A nitr ogen ……….. has electr on arrangement of …………. // A nitr ogen atom has ………… va lence electr ons. A nitr ogen atom needs ………. more e lectr ons to achieve the …………. electr on arrangement // ………… arr angement. A hydrogen …………. has electr on arrangement of …………. // A hydrogen atom has ……… …. valence electr on. Each hydrogen atom needs ……….. more electr on to achieve the …………. electr on arrangement // ………… arr angement. Each of the three hydrogen atoms contr ibutes ………… electr on and one nitr ogen atom contr ibutes ………… electr ons for ………………. to f or m a covalent compound, NH3

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4.3 PREPAR ATIO N OF SALT: I NSOLBULE SALT Guided Exer cise

Exer cise

1. Descr ibe the pr e par ation of lea d(II) chlor ide in the la bor atory. In your descr iption, include the chemical equation involved.

2. Des cr ibe the pr e par ation of calcium su lphate in the la bor atory. In your descr iption, include the chemical equation involved.

Ans wer :

Answer :

Substances : ……………………………………solution, ……………………………………solution, ……………………. water Apparatus: …………………. cylinder , beaker, f ilter f unnel, f ilter ……………

Pr ocedur e: 3 -3 1. ……… 50 cm of ……. mol dm lea d(II) nitr ate solution into a bea k er . 3 -3 2. Add ……… cm of 1.0 mol dm s odium chlor ide solution. 3. ………… the mixtur e with a glass r od. 4. …………. the mixtur e. 5. …………. the salt / pr ec ipita te with distilled water . 6. ………. the s alt by pr e ss ing between pieces of f ilter pa per .

Equation: Pb(NO3)2 + NaCl →

+

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4.4 PREPAR ATIO N OF SALT: SOLUBLE SALT Guided Exer cise

1. Descr ibe the pr e par ation of copper(II) su lphate in the la bor a tory. In your descr iption, include the chemical equation involved.

Exer cise

2. Des cr ibe the pr e par ation of zinc nitr a te in the la bor atory. In your descr iption, include the chemical equation involved.

Ans wer :

Substances : ……………… acid, copper(II) ……………… // copper(II) …………….. // copper(II) ……………. powder, …………….. water

Apparatus: ……………… cylinder , beaker, s patula, ……….. rod, ….……………….. dish, ………….. bur ner , tr ipod stand, wir e gauze, f ilter …………., f ilter pa per

Pr ocedur e: 3 -3 1. ……… 50 cm of 1.0 mol dm su lphur ic acid into a beaker. ………… the su lphur ic acid. 2. Use a s patula to add ………………… powder a little at a time into the acid. ……….. t he mixtur e with a glass r od. 3. Continue adding copper(II) oxide until some of it no longer ……………. 4. …………. the solution into an eva por ating dish to remove the unreacted copper(II) oxide. 5. ………… the s olution until the f inal volume is 1/3 the initial volume // to produce a satur ated solution. 6. ……….. the saturated s olution until crys tals are f or me d. 7. ………….. the s olution to obtain the copper(II) su lphate crystals . 8. …………… the crystals with a little ………… distilled water . 9. ………….. the crys tals by pr ess ing between 2 pie ce s of …………… pa per .

Equation: CuO + H2SO4

→

+

5 3 e

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4.5

RATE OF REACTIO N : Guided Exer cise

1.

Exer cise

2.

Ex per ime nt I R ea cta nts: 3 100 cm of -3 0.5 mol dm HCl, excess CaCO3 ch ips

Ex pe r iment II R ea ctants: 3 100 cm of -3 1.0 mol dm HCl, excess CaCO3 ch ips

Compare the rate of r ea ction in Ex per iment I and II. (i) Which e x per iment has a higher rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er e nce to the collision theory.

Ans wer :

Ex per iment I R ea ctants: 3 50 cm of -3 1.0 mol dm H2 SO 4 , excess gr anulated zinc

Ex per iment II R ea ctants : 3 50 cm of -3 1.0 mol dm H2 SO 4 , excess zinc powder

Compare the rate of r ea ction in Ex per iment I and II. (i) Which ex per iment has a highe r rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er ence to the collision theory. Answer :

(i) Rate of r ea ction in Ex pe r iment ……. is higher than Ex per iment …………

(i) Rate of r ea ction in Ex per iment …….is highe r than Ex per iment ………...

(ii) The concentr ation of acid / …………. ions in in Ex per iment II is ……….. than Ex per iment I.

(ii) In Ex per ime nt II, zinc powder has a ………… total sur fa ce area exposed to ……………….. than gr a nulated zinc in Ex per iment I.

+

The number of H ions per unit ……….. in Ex per iment II is ………….. than Ex per iment I.

Frequency of collision between ………… ions and………………..in Ex per iment II is ………... than in Ex per iment I.

Frequency of collision between ………… ions and …………….. atoms in Ex per iment II is …………… than in Ex per iment I. Frequency of ……………….. collis ion in Ex per iment II is higher than in Ex per iment I.

Frequency of ……………….. collision in Ex per iment II is highe r than in Ex per ime nt I.

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SPM CHEMISTR Y

Guided Exer cise

3.

Exer cise

4.

Ex per ime nt I R ea cta nts: 3 50 cm of -3 0.1 mol dm sodium thiosu lphate solution, 3 -3 5 cm of 1 mol dm su lphur ic acid, o Temperature: 30 C

Ex pe r iment II R ea ctants: 3 50 cm of -3 0.1 mol dm sodium thiosu lphate s olution, 3 -3 5 cm of 1 mol dm s u lphur ic a cid, o Temperature: 45 C

Ex per iment I R ea ctants: 3 50 cm of -3 1.0 mol dm H2 SO 4 , excess zinc powder

Ex per iment II R ea ctants : 3 50 cm of -3 1.0 mol dm H2 SO 4 , excess zinc powder CuSO 4 solution

Compare the rate of r ea ction in Ex per iment I and II. Compare the rate of r ea ction in Ex per iment I and II. (i) Which e x per iment has a higher rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er e nce to the collision theory. Ans wer : (i) Rate of r ea ction in Ex pe r iment II is ………… than Ex per iment I. (ii) ……………… of r ea ction in Ex per iment II is higher than Ex per ime nt I +

…………. energy of H ions and S2O3 2- ions in Ex per iment II is higher than Ex pe r iment I. +

The H ions move ………. and ………. mor e 2of ten with S 2O 3 ions in Ex pe r iment II is than in Ex per iment I.

Frequency of …………….. between ………. ions and ………………. ions in Ex per iment II is higher than Ex per iment I. Frequency of …………………. collision in Ex per iment II is ……….. than in Ex per iment I.

(i) Which ex per iment has a highe r rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er ence to the collision theory.

Answer : (i) Rate of r ea ction in Ex per iment II is …………… than Ex per iment I. (ii) Copper(II) su lpha te solution in Ex per iment II acts as a …………….. whereas no catalyst is used in Ex per ime nt I

In Ex pe r iment II, the presence of cata lyst ena bles the r ea ction to take place through an …………… path which r equir es a …………. activation ener gy. In Ex pe r iment II, more …………….. ions and ................ atoms are a ble to a chieve the ……………… activation energy than Ex per iment I.

Frequency of ………………….. collision in Ex per iment II is ………….than in Ex per iment I.

.

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REVISION MODULE FOR THE MASTERY OF THE BASICS IN SPM CHEMISTR Y

SPM CHEMISTR Y 4.6

HEAT OF COMBUSTIO N Heat of com bustion is the heat change when one mole of alcohol is com pletely burnt in oxygen under standard conditions .

Des cr ibe a la bor atory ex per iment to deter mine the heat of com bus tion of ethanol, C2H5OH. In your descr iption, include the f ollowing: [R elative atomic mass : C=12 ; O=16 ; H =1]

diagr am showing the set-up of a ppa r atus procedures of the ex per ime nt ta bula tion of data o calculation to obtain the heat of com bustion o Two pr ecautiona ry steps taken to obta in more accurate r esult o Answer : o o

ther mometer Wind shield

Copper can water

Tr ipod stand

e thanol

S pir it p

Wooden block

Pr ocedur e: 3 1. Mea sur e 100 cm of ………… and pour into a ………….. can. The copper can is placed on a tr ipod sta nd. 2. Record the ………….. temperature of the wa ter . 3. We igh a s pir it lam p with …………… and record its ………. 4. Place the s pir it la m p under the ……….. can and …….… the w ick of the lam p immediately. 5. …………… the water in the can continuously throughout the ex per iment 0 6. Put out the f lame when the temperature of the water …………… by about 30 C 7. Record the …………… temperature reached by the water . 8. We igh the s pir it lam p and its content ………………… and record the mass .

Ta bula tion of Data: o

The highe st temperature of …………. / C o

T2

The initia l temperature of ………… / C

T1

…………… of s pir it lam p and its content af ter bur ning / g

m2

………….. of s pir it lam p and its content bef or e bur ning / g

m1

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Calculation s te ps: o

Incr ea se in temperature of water

=

……………… C

Ma ss of etha nol burnt

=

……………… g

m Number of mole of C2H5OH

=

46

n

=

The heat energy give n out dur ing com bustion by ethanol = the heat energy absorbed by w ate r = mc = …………….. = x J Heat of com bustion of etha nol, ∆H = - mc n

J mol

-1

= ………….. J mol

-1

Two pr ecautionary ste ps taken to obtain more accur ate r esult: 1. 2. 3. 4.

Make sure the f lame touches the ………….. of the copper can // Place the s pir it la m p very close or jus t beneath the ………….. of the copper can. Stir the water in the copper can ………………. throughout the ex per ime nt. ………… the s pir it lam p and its content …………………. when the f lame has been put out. Use a wind ………… dur ing e x per iment.

[Any two]

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5. WR ITTE N PR ACTICAL PAPER – PAPER 3 5.1

STRUCTURE QUESTIO NS

5.2

ESSAY QUESTIO NS

By : FELIX NGUI SMK TABUAN JAYA , K UCHI NG

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Answer all the questions.

The time suggested for answering Question 1 is 45 minutes.

1

A student carried out an experiment to construct the electrochemical series by measuring the voltage of copper and metal T in a simple voltaic cell as shown in Diagram 1.1. The experiment is repeated by replacing metal T with metals P, Q, R and S.

T

Cu

Copper(II) sulphate solution DIAGRAM 1.1 The voltmeter readings for each pair of metals are shown in Diagram 1.2

DIAGRAM 1.2 (a)

Based on Diagram 1.2, record the voltmeter readings for each pair of metals in Table 1.1.

Pair of metals

Negative terminal

Cu and P

P

Cu and Q

Q

Cu and R

Cu

Cu and S

S

Cu and T

Cu

Voltage / V

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[3 marks]

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(b) Based on the voltmeter readings, arrange the metals Cu, P, Q, R, S and T in descending order of electropositivity.

Descending order of electropositivity of metal. [3 marks]

(c)

Complete Table 1.2 for the experiment. Var iables (i)

Manipulated variable:

Action to be tak en (i) The way to manipulate variable:

...........................................................

.................................................................

...........................................................

................................................................

(ii) Responding variable:

(ii) What to observe in the responding variable:

……………………………..............

.................................................................

……………………………..............

.................................................................

(iii) Controlled variable:

(iii) The way to maintain the controlled variable:

..........................................................

.................................................................

…………………………………......

.................................................................

TABLE 1.2 (d)

[6 marks]

State a hypothesis for this experiment. ................................................................................................................................... ................................................................................................................................... [3 marks ]

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(e)

State three observations and corresponding inferences that can be obtained from the cell in Diagram 1.1(Cu and metal T). O bser vation

Infer ence

1 ……………………………………..

1 ……………………………………..

……………………………………….

……………………………………….

……………………………………….

……………………………………….

2 ……………………………….…….

2 ……………………………………..

………………………………….……

……………………………………….

……………………………………….

……………………………………….

3 ……………………………………..

3 ……………………………………..

……………………………………….

……………………………………….

……………………………………….

………………………………………. [6 mar k s]

(f)

Predict the voltage of the cells which contain the following pair of metals..

Pair of metals

Voltage/ V

P and S P and T Q and R [3 mar k s] (g) Classify metals P, Q, R, S and T into more electropositive than copper and less electropositive than copper. Write your answers in the table provided.

[3 mar k s]

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(h) Explain why the voltage of cell of copper and metal S is larger than the cell of copper and metal P. ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... [3 mar k s] (i)

Another example of a chemical cell is Daniell Cell. Draw the apparatus set-up of the Daniell Cell of copper and metal T.

[3 mar k s]

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2.

A student carried out an experiment to investigate the effect of concentration on the rate of 3 -3 3 reaction. He poured 50cm of 0.5 mol dm sodium thiosulphate solution into a 250 cm conical flask. The conical flask was then placed on a mark “X” on a piece of white paper. 3

-3

10.0 cm of 1.0 mol dm hydrochloric acid was added to the sodium thiosulphate solution and shaken. At the same time, the stopwatch was started. The stopwatch was stopped as soon as the mark “X” on the piece of white paper was no longer visible. The student repeated the experiment using sodium thiosulphate solution with the concentration -3 -3 -3 -3 of 1.0 mol dm , 1.5 mol dm , 2.0 mol dm and 2.5 mol dm . Diagram 2 shows the readings of the stopwatch for each of the reactions at different concentrations.

Diagram 2 (a)

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Record the time for each reaction in the spaces provided in Diagram 2.

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[3 marks]

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(b)

Construct a table and record the concentration, time and

1 time

of this experiment. [3 mar k s]

(c)

State the operational definition for rate of reaction for this experiment. …………………………………………………………………………………………….. ……………………………………………………………………………………………..

…………………………………………………………………………………………….. [3 marks] 1 (i) Draw a graph of concentration against on a graph paper. (d) time [3 marks] (ii) Using the graph drawn in (b)(i), state the relationship between concentration and the rate of reaction. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [3 marks] (e)

(f)

Predict the time taken for the mark “X” to be no longer visible if the experiment is -3 repeated using 3.0 mol dm sodium thiosulphate solution. …………………………………………………………………………………………….. [3 marks] State one observation for the experiment. Explain your answer. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [3 marks]

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(g) Suggest a hypothesis for this experiment. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [3 marks]

(h)

Var iables (i)

Manipulated variable:

Action to be tak en (i) The way to manipulate variable:

...........................................................

......................................................................

...........................................................

.......................................................................

(ii) Responding variable:

(ii) What to observe in the responding variable:

……………………………...............

.......................................................................

……………………………...............

…...................................................................

(iii) Controlled variable:

(iii) The way to maintain the controlled variable:

…………………………………….

…………………………………………….

……………………………………..

…………………………………………….. [6 marks]

(i)

The relationship between concentration and rate of reaction can be applied in our daily life. Using your knowledge of chemistry, explain why fanning glowing charcoal will cause the charcoal to ignite. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [3 marks]

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3.

“If iron is exposed to oxygen and water, rusting will occur but if iron is in contact with a more electropositive metal, rusting is inhibited. “ Plan a laboratory experiment to investigate the effect of other metals on the rusting of iron. Your planning should include the following aspects:

(a) Statement of the problem (b) (c) (d) (e) (f)

All the variables Statement of the hypothesis List of substances and materials Procedure of the experiment Tabulation of data (17 marks)

4.

“Vulcanised rubber is more elastic than unvulcanised rubber.”

Plan a laboratory experiment to compare the elasticity of vulcanised rubber and unvulcanised rubber. Your planning should include the following aspects:



5. “Soaps and detergents are cleansing agents but their effectiveness in hard water is different.”

In an experiment to compare the effectiveness of a soap and a detergent in hard water. Your planning should include the following aspects:



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6. SUGGESTED ANSWER S

6.1 GUIDED ESSAY WRITING FOR PAPER 2

6.2 WR ITTE N PR ACTICAL PAPER

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6.1 GUIDED ESSAY WRITING FOR PAPER 2

6.1.1

CHEMICAL BONDS: IONIC BO ND Guided Exer cis e

Exer cise

1.

2.

Element Proton num ber A 3 B The r ea ction between atoms A and 9B f or ms a n ionic com pound.

Element Proton num be r C 12 D The r ea ction between atoms C and8 D f or ms an ionic com pound.

(i) Ex plain how this ionic compound is f or med. (ii) Draw the ele ctr on arrangement of t he compound f or med.

(i) Ex plain how this ionic compound is f or med. (ii) Draw the ele ctr on arrangement of the compound f or med.

Answer : (i) Atom A has electr on arrangement of 2.1. To achieve the sta ble electr on arrangement // duplet arrangement, atom A donates one + vale nce electr on and a positive ion, A is f or med. + [A → A + e ]

Answer : (i) Atom C has electr on arrangement of 2.8.2 To achieve the sta ble electr on arrangement // octet arrangement, atom C donates two va lence 2+ electr ons and a positive ion, C is f or med. 2+ [ C → C + 2e ]

Atom B has electr on arrangement of 2.7. To achieve the sta ble electr on arrangement // octet arrangement, atom B r eceives one ele ctr on and a negative ion, -B is f or med. [B + e → B ]

Atom D has electr on arrangement of 2.6. To achieve the sta ble electr on arrangement // octet arrangement, atom C r eceives two 2D is f or med. electr ons and a negative ion, 2[ D + 2e → D ]

+

-

2+

2-

A and B ions are attracted to each other by ele ctr ostatic f or ces to f or m an ionic c om pound AB.

C and D ions are attracted to each other by electr ostatic f or ces to f or m an ionic com pound CD.

(ii)

(ii)

_

+ X X

X X

XX X

X

X X XX

+

2+ X X

XX X X XX 2+-

A

C B

X X

2X X

XX X X XX

D

X X

2--

-

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6.1.2

CHEMICAL BONDS: COVALENT BO ND Guided Exer cise

Exer cise

1.

2.

Element Proton num ber N 7 H 1 The r ea ction between nitr ogen and hydr ogen atoms f or ms a covale nt com pound.

Eleme nt Proton num ber C 6 Cl 17 The r ea ction between carbon and chlor ine atoms f or ms a covalent com pound.

(i) Ex plain how this covalent compound is f or med (ii) Draw the e lectr on arrangement of the compound f or med.

(i) Ex plain how this cova lent compound is f or med (ii) Draw the electr on arrangement of the compound f or med.

Ans wer : A nitr ogen atom has electr on arrangement of 2.5 // A nitr ogen atom has f ive valence electr ons. A nitr ogen atom needs three more ele ctr ons to achieve the sta ble electr on arrangement // octet arr a ngement.

Answer : A carbon atom has electr on arrangement of 2.4 // A carbon atom has f our v alence electr ons. A carbon atom needs f our more ele ctr ons to achie ve the sta ble electr on arrangement // octet arr angement.

A hydrogen atom has electr on arrangement of 1 // A hydrogen atom has one va lence electr on. Each hydrogen atom needs one more e lectr on to achieve the sta ble electr on arrangement // octet arr a ngement.

A chlor ine atom has electr on arrangement of 2.8.7 // A chlor ine atom has seven valence electr ons. Each chlor ine atom needs one more e lectr on to achieve the sta ble ele ctr on arrangement // octet arr angement.

Each of the three hydrogen atoms contr ibutes one electr on and one nitr ogen atom contr ibutes three electr ons for sha r ing to f or m a covalent compound, NH3

Each of the f our chlor ine atoms contr ibutes one electr on and one carbon atom contr ibutes f our electr ons for shar ing to f or m a covalent compound, CCl4

H

H

X X

XX X

N N X XX

XX XX X XX XX X XX C XX XX XX X X X XX X XX X Cl X XX XX X XX XX

XX XX X X

H XX XX

X XX X X

Cl

X XX XX

XX XX X

Cl

X XX X X

XX XX X XX XX

Cl

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6.1.3

PR EPAR ATIO N OF SALT: I NSOLBULE SALT Guided Exer cise

Exer cise

1. Descr ibe the pr e par ation of lea d(II) chlor ide in the la bor atory. In your descr iption, include the chemical equation involved.

2. Des cr ibe the pr e par ation of calcium su lphate in the la bor atory. In your descr iption, include the chemical equation involved.

Ans wer :

Answer :

Substances : Lea d(II) nitr ate solution, sodium chlor ide s olution, distilled wate r

Subs tances: Calcium nitr ate solution, sodium s u lphate s olution, dis tilled water

Apparatus: Mea sur ing cylinde r , beaker, f ilte r f unne l, f ilter pa per

Apparatus: Mea sur ing cylinder , beaker, f ilter f unnel, f ilter pa per

Pr ocedur e: 3 -3 1. Pour 50 cm of 1.0 mol dm lea d(II) nitr ate solution into a bea k e r . 3 -3 2. Add 100 cm of 1.0 mol dm sodium chlor ide solution. 3. Stir the mixtur e with a glass r od. 4. Filter the mixtur e. 5. R inse / wash the sa lt / pr e c ipitate with distilled water . 6. Dry the s alt by pr ess ing between 2 piece s of f ilter pa per .

Pr ocedur e: 3 -3 1. Pour 50 cm of 1.0 mol dm calcium nitr ate s olution into a bea k er . 3 -3 2. Add 50 cm of 1.0 mol dm s odium s u lphate s olution. 3. Stir the mixtur e with a glass r od. 4. Filter the mixtur e. 5. R inse / wash the salt / pr ec ipitate with dis tilled water . 6. Dry the salt by pr ess ing between 2 pieces of f ilter pa per .

Equation: Pb(NO3)2 + 2 Na Cl → P bCl2 + 2 Na NO3

Equation: Ca(NO3)2 + Na2SO4 → CaSO4 + 2 Na NO3

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6.1.4

+

+

PREPAR ATIO N OF SALT: SOLUBLE SALT (NOT Na , K+ OR NH 4 SALT)

Guided Exer cise 1. Descr ibe the pr e par ation of copper(II) su lphate in the la bor a tory. In your descr iption, include the chemical equation involved.

Exer cise 2. Des cr ibe the pr e par ation of zinc nitr a te in the la bor atory. In your descr iption, include the chemical equation involved.

Ans wer :

Answer :

Substances : Su lphur ic a cid, copper(II) oxide // copper(II) carbonate // copper(II) hydr oxide powder , distilled wate r

Subs tances: Nitr ic acid, zinc // zinc oxide // zinc carbonate // zinc hydr oxide powder, distilled water

Apparatus: Mea sur ing cylinder , beaker, s patula, glass r od, eva por ating dish, Bunsen burner, tr ipod s tand, wir e gauze, f ilter f unne l, f ilter pa pe r

Apparatus: Mea sur ing cylinder , beaker, s patula, gla ss r od, eva por ating dish, Bunsen burner, tr ipod sta nd, wir e gauze, f ilter f unnel, f ilter pa per

Pr ocedur e: 3 -3 1. Pour 50 cm of 1.0 mol dm s u lphur ic acid into a beaker. Warm the s u lphur ic a cid. 2. Use a s patula to add copper(II) oxide powder a little at a time into the acid. Stir the mixtur e with a glass r od. 3. Continue adding copper(II) oxide until some of it no longer diss olves. 4. Filter the solution into an e va por ating dish to remove the unreacted copper(II) oxide. 5. Heat the solution until the f inal volume is 1/3 the initial volume // to produce a satur ate d solution. 6. Cool the saturated solution until crystals ar e f or med. 7. Filter the solution to obtain the copper(II) su lphate crystals . 8. R inse the crystals with a little cold dis tilled water . 9. Dry the crystals by pr ess ing between 2 pieces of f ilter pa per .

Pr ocedur e: 3 -3 1. Pour 50 cm of 1.0 mol dm nitr ic acid into a beaker. Warm the nitr ic a cid. 2. Use a s patula to add zinc oxide powder a little at a time into the acid. Stir the mixtur e with a glass r od. 3. Continue adding zinc oxide until some of it no longer diss olves. 4. Filter the solution into an eva por ating dis h to remove the unreacted zinc oxide. 5. Heat the solution until the f inal volume is 1/3 the initial volume // to produce a satur ated s olution. 6. Cool the saturated s olution until crystals ar e f or med. 7. Filter the solution to obtain the zinc nitr ate crys tals. 8. R ins e the crys tals with a little cold dis tilled water . 9. Dry the crys tals by pr ess ing between 2 piece s of f ilter pa per .

Equation: CuO + H2SO4 → CuSO4 + H2O

Equation: ZnO + 2HNO 3 → Zn(NO3)2 + H2O

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6.1.5

RATE OF R EACTIO N : Guided Exer cise

Exer cise

1.

2.

Ex per ime nt I R ea cta nts: 3 100 cm of -3 0.5 mol dm HCl, excess CaCO3 ch ips

Ex pe r iment II R ea ctants: 3 100 cm of -3 1.0 mol dm HCl, excess CaCO3 ch ips


Ex per iment I R ea ctants: 3 50 cm of -3 1.0 mol dm H2SO4 , excess gr anulated zinc

Ex per iment II R ea ctants : 3 50 cm of -3 1.0 mol dm H2SO4 , excess zinc powder

Compare the rate of r ea ction in Ex per iment I and II. (i) Which ex per iment has a highe r rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er ence to the collision theory.

Answer:

Answe r:

(i) Rate of r ea ction in Ex pe r iment II is highe r than Ex per iment I.

(i) Rate of r ea ction in Ex per iment II is higher than Ex per iment I.

(ii) The concentr ation of acid / hydrogen ions in in Ex per iment II is higher than Ex pe r iment I. +

The number of H ions per unit volume in Ex per iment II is highe r than Ex per iment I. +

Frequency of collision between H ions a nd CaCO3 in Ex per iment II is higher than in Ex per iment I.

(ii) In Ex pe r iment II, zinc powder has a lar ger total sur f ace area exposed to collision than gr anulated zinc in Ex per iment I. +

Frequency of collision between H ions and zinc atoms in Ex pe r iment II is higher than in Ex per iment I. Frequency of eff ective collis ion in Ex per iment II is higher than in Ex per iment I.

Frequency of eff ective collision in Ex per iment II is highe r than in Ex per ime nt I.

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SPM CHEMISTR Y Guided Exer cise

Exer cise

3.

4.

Ex per ime nt I R ea cta nts: 3 50 cm of -3 0.1 mol dm sodium thiosu lphate solution, 3 -3 5 cm of 1 mol dm su lphur ic acid, o Temperature: 30 C

Ex pe r iment II R ea ctants: 3 50 cm of -3 0.1 mol dm sodium thiosu lphate s olution, 3 -3 5 cm of 1 mol dm s u lphur ic a cid, o Temperature: 45 C


Ex per iment I Subs tance s: 3 50 cm of -3 1.0 mol dm H2SO4 , excess zinc powder

Ex per iment II Substances : 3 50 cm of -3 1.0 mol dm H2SO4 , excess zinc powder , CuSO 4 solution

Compare the rate of r ea ction in Ex per iment I and II. (i) Which ex per iment has a highe r rate of r ea ction? (ii) Ex plain your answer in (i) with r ef er ence to the collision theory.

Answer:

Answe r:

(i) Rate of r ea ction in Ex pe r iment II is highe r than Ex per iment I.

(i) Rate of r ea ction in Ex per iment II is higher than Ex per iment I.

(ii) Temperature of r ea ction in Ex per iment II is higher than Ex per ime nt I

(ii) Copper(II) su lpha te solution in Ex per iment II acts as a catalys t whereas no catalys t is used in Ex per iment I

+

2-

K inetic energy of H ions and S 2O 3 ions in Ex per iment II is highe r than Ex per iment I. +

The H ions move f as ter and collide mor e 2of ten with S2O3 ions in Ex pe r iment II is than in Ex per iment I. +

Frequency of collision between H ions a nd 2S2O3 ions in Ex per iment II is higher than in Ex per iment I. Frequency of eff ective collision in Ex per iment II is highe r than in Ex per ime nt I.

In Ex pe r iment II, the presence of cata lyst ena bles the r ea ction to take place through an alter native path which r equir es a lowe r activation ener gy. +

In Ex pe r iment II, more H ions and zinc atoms are a ble to achie ve the lower activation energy than Ex per iment I.

Frequency of eff ective collis ion in Ex per iment II is higher than in Ex per iment I.

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SPM CHEMISTR Y 6.1.6

HEAT OF COMBUSTIO N Heat of com bustion is the heat change when one mole of alcohol is com pletely burnt in oxygen under standard conditions . Des cr ibe a la bor atory ex per iment to deter mine the heat of com bus tion of ethanol, C2H5OH. In your descr iption, include the f ollowing: [R elative atomic mass : C=12 ; O=16 ; H =1]

diagr am showing the set-up of a ppa r atus procedures of the ex per ime nt ta bula tion of data o calculation to obtain the heat of com bustion o Two pr ecautionary steps taken to obta in more accurate r esult o Ans wer: o o

Ther mometer

Wind shield Copper can

wate r

P ipe clay tr iangle

ethanol S pir it lam p Wooden block

Pr ocedur e: 3 1. Mea s ur e 100 cm of water and pour into a copper can. The copper can is pla ce d on a tr ipod sta nd. 2. Record the initial temperature of the water . 3. Weigh a s pir it lam p with ethanol and record its mass . 4. Place the s pir it la m p under the copper can and light the wick of the lam p immediately. 5. Stir the water in the can continuously throughout the ex per iment. 0 6. Put out the f lame when the temperature of the water incr ea ses by about 30 C. 7. Record the highest temperature reached by the water . 8. Weigh the s pir it lam p and its content immedia tely and record the mass . Ta bula tion of Data: o

The highe st temperature of water / C o

T2

The initia l temperature of water / C

T1

Mass of s pir it la m p and its content af ter bur ning / g

m2

Mass of s pir it la m p and its contents bef or e bur ning / g

m1

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Calculation ste ps : o

Incr ea se in temperature of water

=

(T2 - T1) C

Mass of ethanol burnt

=

(m1 - m2) g

m Number of mole of C2H5OH

=

46

= n

The heat energy given out dur ing com bus tion by e thanol = the heat energy absorbed by w ater = mc = mc(T2-T1) = x J Heat of com bustion of ethanol, ∆H = - mc n = - x n

J m ol

J mol

-1

-1

Two pr ecautionary ste ps taken to obtain more accur ate r esults: 1. Make sure the f lame touches the base of the copper can // Place the s pir it la m p very clos e or just beneath the base of the copper can. 2. Stir the water in the copper can continuous ly throughout the ex per iment. 3. We igh the s pir it lam p and its content immediately when the f lame has been put out. 4. Use a wind shield dur ing ex per iment. [Any two]

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6.2

MARKING SCHEME CHEMISTRY PAPER 3

Question 1(a)

R ubr ic [Able to record all the five readings accur ately]: Suggested answer : Pairs of electr odes

1 (b)

Scor e

Voltage/V

Cu and P

1.5

Cu and Q

1.7

Cu and R

0.5

Cu and S

2.3

Cu and T

1.2

3

[Able to arrange the position of all metals in descending order of electropositivity corr ectly] 3

Suggested answer : S, Q, P, Cu, R, T 1 (c)

[Able to state three variables and the way to control them c orr ectly] Suggested answer : Manipulated var ia ble: Pair of metals

Substituting the electrode T with different metals // P, Q, R, S and T

Responding var ia ble: Voltmeter reading

Reading of the voltmeter// voltage

6

Controlled var ia ble:

1 (d)

Electrolyte / copper(II) sulphate solution // concentration and volume of electrolyte //

Use the same electrolyte / concentration of electrolyte / CuSO4 //

same voltmeter //

use the same voltmeter //

copper electrode

use copper electrode in all experiments.

[Able to state the relationship between the manipulated variable and the responding variable and the direction c orr ectly] Suggested answer : The further apart / the distance of the pair of metals in the electrochemical series, the higher is the voltage / the voltmeter reading.

3

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Question 1(e)

Ex planation [Able to state thr ee observations and thr ee infer ences corr ectly] O bser vation

Inf er ence

1. Copper strip / rod / metal

Copper is oxidised / loses electron to form copper(II) ion // Copper is more electropositive than P.

dissolves / becomes thinner

2+

2. Brown solid is deposited at

6

Copper is formed // Cu is reduced to copper

metal T

2+

3. The intensity of the blue

The concentration of Cu in the solution remain unchanged // the 2+ rate of Cu formed at anode is the same as the rate of discharge of 2+ Cu at the cathode.

coloured solution remains unchanged

1(f)

SPM CHEMISTR Y Maximum scor e

[Able to predict the voltage of the three cells accur ately] Suggested answer:

1(g)

Pair of metals

Voltage/ V

P and S

0.8

P and T

2.7

Q and R

2.4

3

[Able to classify all the metals cor re ctly] 3

Suggested answer:

1(h)

More electr opositive

Less electr o positive

P, Q, S

R, T

[Able to explain the difference in the voltage of the cell] Suggested answer:

3

The distance between Cu and metal S is further / greater than the distance between Cu and metal P in the electrochemical series.

[Able to draw the labeled apparatus set-up completely] 1(i)

Suggested answer:

Copper

Metal T

Copper(II) sulphate solution

T nitrate solution Salt br idge

3

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SPM CHEMISTR Y Question 2 ( a) ( b)

R ubr ic

Scor e

[Able to record all the five readings accurately to one decimal point]: t1 = 55.0 s, t2 = 48.0 s, t3 = 42.0 s, t4 = 37.0 s, t5 = 33.0 s,

3

[Able to construct a table and tr ansf er all the five readings from (a) corr ectly with unit for each heading.. The values for

1 time

must be given to thr ee

decimal places]. Concentration /

Time / s

1

-3

mol dm

(c)

time

0.5

55.0

0.018

1.0

48.0

0.021

1.5

42.0

0.024

2.0

37.0

0.027

2.5

33.0

0.030

[Able to give the operational definition corr ectly] Rate of reaction is inversely proportional to the time taken for the mark

3

3

1

“X” to be no longer visible // Rate of reaction (d)

-1

/s

time

[ Able to do the f ollowing: Draw a graph of suitable size / using suitable scale (occupying a bout 75% of graph pa per ) Label the axes concentration / mol dm

-3

and

1 time

-1

/s

3

Plot the five points correctly from the table constructed in (b) Draw a straight line (linear) graph ] -3 (i) concentration / mol dm 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01

1 -1 /s time

0 0.01

0.02

0.03

0.04

0.05


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SPM CHEMISTR Y (d)

[ Able to state the relationship between concentration and the

rate of reaction corr ectly] (ii) An increase in concentration (of sodium thiosulphate solution) will

3

increase the rate of reaction. (e)

[Able to predict the time taken using the graph dr awn] Suggested answer :

(f)

30 s

3

[Able to state and explain the observation c orr ectly.] A yellow precipitate is formed. The reaction of hydrochloric acid and sodium thiosulphate solution produces sulphur, sulphur dioxide and water. // The sulphur produced from the reaction forms the yellow precipitate.

(g)

[Able to state the relationship between the manipulated variable and the responding variable and the direction c orr ectly]

3

3

The higher / lower the concentration of sodium thiosulphate solution, the shorter / longer the time taken for the mark “X” to be no longer visible.

(h)

[Able to state three variables and the way to control them c orr ectly] Suggested answer : Manipulated var ia ble: Concentration of sodium thiosulphate solution

Responding var ia ble: Time taken for the mark “X” to be no longer visible // Rate of reaction

Repeat the experiment using sodium thiosulphate solution with -3 concentrations of 1.0 mol dm , -3

-3

1.5 mol dm , 2.0 mol dm and -3 2.5 mol dm . Time taken for the mark “X” to be no longer visible

6

Controlled var ia ble: Temperature of sodium thiosulphate solution // size of conical flask // concentration and volume of hydrochloric acid used // total volume of reacting mixture

Solutions of same temperature are used // use conical flasks of same size // use the same concentration and volume of hydrochloric acid // keep the total volume of reacting mixture the same.

Reject : Use of “Quantity” or “amount of “ hydrochloric acid / reacting mixture.

(i)

[Able to explain phenomena using relevant knowledge of chemistry] Suggested answer : Fanning increases the concentration of oxygen blown over glowing charcoal // Fanning causes the glowing charcoal to be exposed to more oxygen. Thus, the glowing charcoal ignites.


3

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SPM CHEMISTR Y Question

R ubr ic

Scor e

3(a)

How do different metals in contact with iron affect the rusting of iron? // What is the effect of different metals in contact with iron on the rusting of iron nails ?

3

( b)

Iron nail rusts when it is in contact with a less electropositive metal. Iron nail does not rust when it is in contact with a more electropositive metal

3

(c)

MV : Different metals in contact with iron nail RV: Rusting of iron

3

CV: Type of (iron) nail, medium in which iron nail is kept, temperature (d)

(e)

(f)

Name one metal mor e electr o positive (m agnesium) than iron and one metal less electr o positive (copper ) than ir on. Materials : Iron nails, magnesium ribbon, copper foil, hot jelly solution containing potassium hexacyanoferrate(III) solution, sandpaper. Apparatus : test tubes, test tube rack,

Procedure : 1. Clean / Rub three iron nails with s andpa per . 2. Two iron nails are coiled / wound separately with magnesium ribbon and copper foil. 3. The three nails are each put / di p / immer sed into labelled test tubes A, B and C containing hot jelly solution with potassium hexacyanoferrate(III) solution separately . 4. The test tubes are put on a test tube rack under room condition fo r a f ew days. 5. The test tubes are observed and the results are recor ded.

3

3

Ta bulation of data : Suggested answer(any one )

Pair of metal

O bser vation

Iron nail only Iron nail coiled with magnesium ribbon Iron nail coiled with copper foil 3 Tets tube

Pair of metal

A

Iron nail only

B

Iron nail coiled with magnesium ribbon

C

Iron nail coiled with copper foil

O bser vation

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SPM CHEMISTR Y Question 4 ( a)

R ubr ic

Scor e

Is vulcanised rubber more elastic than unvulcanised rubber ? // How does the elasticity of vulcanised rubber differ from unvulcanised rubber ? //

3

Does vulcanisation increase the elasticity of rubber? ( b)

MV : Types of rubber // Vulcanised and unvulcanised rubber RV: Length of rubber strip

3

CV : Size of rubber strip, mass of weight (c)

Vulcanised / Unvulcanised rubber is more elastic than unvulcanised / vulcanised rubber.

(d)

Materials : Vulcanised rubber strip, unvulcanised rubber strip

Apparatus: Retort stand and clamp, (bulldog) clips, ruler, 10 g, 20 g,

3

3

30 g , 40 g and 50 g weights, (e)

Procedure : 1. (Using bulldog clips,) hang a vulcanised rubber strip and an unvulcanised rubber strip onto a retort stand each. 2. The (initial) lengths of the two rubber strips are measur ed. 3. A 10 g weight is hung to each of the two strips and the lengths of the two strips are measured and recorded.

3

4. The weights ar e r emoved and the lengths of the rubber strips are measured and recor ded. 5. Steps 3 and 4 are repeated using 20g, 30g, 40g and 50g weights to replace the 10 g weights.

(f)

Tabulation of data Weights /g

Length of vulcanised rubber Length of unvulcanised strip / cm rubber strip / cm Without With Weight Without With Weight weight weight removed weight weight removed

3

10 20 30 40 50

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SPM Chemistry Revision Module on the Basics

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