CAPE Chemistry June 2004 2004 U2 P2 Ql - Answ Answer er l(a)
Concentration Concentr ation of B2.
l(b)
Concentration Concentr ation of o f B •
l(c)(i)
One.
l(c)(ii)
Zero
l(d)
Anyvaue Any vaue in the range 00041-00044
l(e)(i) l(e)(ii)
k = Rate/[A ]. For experiment 1, k = 000141/0 000141/01 1 = 00141s·1
l(f)
Sow step: A 2 2A Faststeps: B 2B 2A + 2B 2AB
CAPE Chemi Chemistry stry June 2004 2004 U2 P2 Q2 - Ans Answer wer 2(a)
Ligand exchange occurs because one system is more stable. CO replaces 02 in complex therefore haemoglobin loses its oxygen carying capacity and body becomes becomes staed of oxygen
2(b)(i)
-Original pale blu blue e solution soluti on -pale blue blue ppt formed. -ppt dissolves -dark -d ark blue solution formed
2(b)(ii)
CAPE Chemistry June 2004 U2 P2 Q3 - Answ Answer er 3(a)(i)
NO/N02•
3(a)(ii)
HN0 2 or HN03 .
3(a)(iii)
NH3
3(a)(iv iv))
2NO + H20 + ½02
3(b)(i)
Concentrations Concentrati ons 1 to 4 respectively are: 1.33, 146, 15 3 and 166
3(b)(ii)
Mean= (1.33 + 146 + 153 + 166)/ 166)/4 4 = 15 mg/L
-
2HN0 2
CAPE Chemistry Chemistry June 2004 2004 U2 P2 Q4 - Ans Answer wer 4(a)
K p= [Ag+] [Cl·].
4 (b)
[Cl·]= ]= 10 x 1 0 3 mol dm· 3 [Ag+]= 1/1000 x 10· 3= 10 x 106 mol dm· 3. [Cl·
s
Ion concentration [Ag•] [Cl ]= 10 x 106 x 10 x 10· 3= 10 10x x 10· 9 mol2 dm dm· · Ion product> K p· Precipitate of silver chloride forms for ms s
4(c)(i)
No. of moles H calculated from results of titration No of moles OH·= No. of mole moless H. [OH] can be calculated. [Ca2•] = ½[OH ] and K p= [Ca2• ] [OH·]2 s
4(c)(ii) 4( c)(ii)
Calculation of no of moles H: (115 x 01)/1000 01)/1000= = 115 x 10· 3. Calculation of [OH]= (115 x 10· 10· 3 x 103)/250 )/250= = 0046 0046 mol dm 3 Calculation of [Ca 2· = 0046/2= 0046/2= 0023 mol dm· 3 0023 3 x (0046) (0 046)2= 4.86 x 105 mol3 d m K p= 002
4(d)
-White ppt of Ca(OH Ca (OH forms -Common ion efec -Addition of con CaCl 2 increases the con of a2 . -Ion product eceeds solubility product -Solubility of Ca(OH decreases
CAPE Chemi Chemistry stry June 2004 2004 U2 P2 QS - An Answe swerr 5(a)
Macroscopic properties are constant under the stated onditions of temp., press pre ss and initial co c o n Microscopic Microscop ic processes continue but are in balance
5(b)
5( c)(i)
Brown colour intensifies
5( c)(ii)
Foard reaction is endothermic Ineasing temperature shif equilibrium position to right to remove the added heat
5(c)(iii)
Colour fades/ligh fades/lightens. tens.
5(c)(iv)
Equilibrium positi p osition on shifs to lef Ineased pressur pressuree favours smaller volume Smaller no of moles of o f gas on lef = smaller no of moles
5(d)(i)
No efect on K"
d)(ii) 5(d)(ii) 5(
Pressure has no efect on KJan equilibrium constant is constant at a particular temp/temp temp/temp has not change changed d Although equilibrium position position shifs shif s to right, [N02] and [N20 ] have both increased. 4
5(e)
= (1(1- 35) = 65 mol mol Equilibrium amt N02
= 2 x 65 = 13 mol
K = (13)/(35) = 4 48 8 mol dm·3.
CAPE Chemistry June 2004 2004 U2 P2 Q6 - Answ Answer er 6(a)
Patern in variation of oxidation num number berss 1 2 3 4 5 6 7 or 1 2 3 4 5 4 3. Correct name names. s. Explanation: E xplanation: the metal meta l elements e lements form ionic ioni c bond bondss wit with h 02 by losing the no of electrons equivalent to the group no and the non-metallic elements elemen ts share the no no of electrons in the outermost shell
6( b)(i)
6( b)(ii) b)(ii) 6( c)(i)
Metal chlorides are expected to be neutral
6( c)(ii)
AICl3 is acidic due to high charge density of Al 3* 10n, an H* 10n from hydrated ion complex complex is easil easily y lost lost
6(d)(i)
Acrosss the period from Na to A the oxides change from basi Acros basicc to amphoteric to acidic Thi Thiss occu occurs rs as the natur naturee of bon bonds ds change from ionic in giant ionic latice structures to ionic/covalent to covalent discrete molecules molecu les
CAPE Chemistry June 2004 2004 U2 P2 Q7 - Answ Answer er 7(a)(i)
-Bonding group IV eleme -Bonding element nt sp3 hybridized. -Overlap of hybrid and atomic orbital orbital of chlorine forms the sigma cova covalent lent bond -Oxidation state of +4 i s too polarizing polarizing to to be ionic
7(a)(ii)
Explanation related to strength of bonds and stability of +2 state Covalent bonds of lead lead are weaker +2 state of lead more stable
7 (b)(i) 7(b)(ii)
-Bonds in SiCl4 are polar -Silicon is electron deficient -Silicon acts as a site for atack by lone pair on oxygen atom of o f water molecule
7(b)(iii)
Polymerization yie yields lds hydrated sili silica ca
7 (c)(i)
-Silica has a giant structure -Strong covalent bonds -Silicon oxide has semi conductor properties -Electron -Electro n mobility increases with temperature
7(c)(ii)
Ceramic would be of lower heat and corrosion resistance Bonds are more susceptible to distortion
CAPE Chemistry June 2004 2004 U2 P2 Q8 - Answ Answer er 8(a)
(i): Carbo Carbon n anode. (ii): Carbon catho cathode de (iii): Colite (Na3AI AIF F6)/Al20 3 (iv):: Molten Al tapped of here (iv)
8(b)
Lower the melting point of the Al203 (2015 strategy
8(c)
t gets oxidized to CO or CO2
8(d)(i)
Al.
.
°c
600
°
C) Energy saving
•
8( d)(ii) 8(e)(i) 8(e)(ii) 8(f)
Pots and pans -Al as a thermal conducto con ductorr Any 1 of the 3 remaining -Al as a thermal insulator Explanation: Structure of Al metal 1ith 3 mobile electrons makes it a good thermal conduct conductor, or, increas increased ed kineti kineticc energ energy y of electrons As a thermal insulator, Al reflects reflects heat inward thereby keeping baby warm w arm or reflects heat from surface keepin keeping g firemen firemen cool or reflecting reflecting car headlights
CAPE Chemistry June 2004 U2 P2 Q9 - Answe Answerr 9(a)(i)
-Vaporization of crud crude. e. Temperature gradient gradient in column -Bubble caps ofer of er surface for condensation -Fractions are tappe tapped d of -More -Mor e volatile fractions ascend column
9(a)(ii)
- Major source source of fuels -Feedstock for petrochemical indust -Industrial solvent -Generally furnished starting materials that chemical industries and production of structural struc tural and engineering materials materials
9(b)
-Concerns due -Concerns du e to exposure to chemicals increa increase se in incidence of work rela related ted cancers -Environmental degradation from chemical pollution eg air quality, water quality
9( c)(i)
Chemical change initiated by absorption of UV radiation radiat ion
c)(i (ii) i) 9( c)
9(c)(iii)
Natural biodegradable of plant or animal material, gasoline stations or vehicular vehicul ar emissions During peak trafic period high acti activity vity due to% of airbo airborne rne hydrocarbons hydrocarbons
CAPE CA PE Chemistry Chemistry Jun June e 2005 U2 P2 Ql - Answ Answer er l(a)(i)a)
If sma quantities of actic acid are produced, then H· ions are removed by reaction with H3- and pH does d oes not change appreciaby.
l(a)(i)b)
If arge quantities of actic acid are produced then the bood oses its bufer capacity and the pH of the bood fas
l(a)(ii)
H· ions from H2C0 3 are used to neutraize the excess akainity and CO2 produced in the tissues dissoves in the pasma pas ma to produc pr oduce e H2C0 3 .
l(b)
used ed to determine the concentrati concentration on of sat and wea weakk acid needed. K vaue us Known mass of sat and weak acid obtained Soution of known concentration prepared mixed Sat dissoved in soution of known acid concentration pH meter is used us ed to to confirm pH of bufer buf er 0
CAPE Chemistry June 2005 2005 U2 P2 Q2 - Answ Answer er 2(a)
-P ut equal volumes -Put vol umes of water into 4 test tubes. Weigh equal quantities of eac each h white solid Shake/stir The Th e one th that at dissolves dis solves completely is MgS04 To identify the others, filter and weigh solids (or allow test tubes to setle and measure height of insoluble component) From least to mos mostt Ca - Ba •
2(b)(i)
Dim light/dark.
2(b)(ii)
Highly exothermi exothermicc possibly burnt
2(b)(iii)
CAPE Chemi Chemistry stry June 2005 U2 P2 Q3 - An Answe swerr 3(a)(i)
Carbohydrate content
3(a)(ii)
Flavour and colour of produc
3{a)(iii)
-Distil equal volumes of the tw two o beverages. Measure volume of alcohol alcohol yielded yielded as a s distillate distillate at the boili boiling ng point of ethanol
3(b)(i)
Stimulates the central neous system system
3(b)(ii)
Ab use impacts negatively on health and therefore on the health Abuse heal th care system Alcohol Alc ohol abuse can lead to depression and a decrease in productivity -Increase -Incr ease in antisocial behaviour becomes evident in i n society soc iety -Breakdown in family fami ly structure
CAPE Chemistry June 2005 U2 P2 Q4 - Answ Answer er 4(a)
-According to BronstedLow BronstedLow theo an an acid is a proton donor do nor Acidity due to COOH group. -Molecule dissociates to yield H· ions due to polarization of the carboyl group Classified as as a weak acid due to incomplete dissociation.
4(b)(i)
HAH•+A pH= pH = log [H• [H•] ] [H]]= antilog326 [H antilog326= = 550 x 104 mol dm3.
4(b)(ii)
[HA]= 20 x 1 0 4 _ 550 x 1 0 4= 195 x 102 mol dm3.
4(b)(iii) b)(iii)
107)/(195 X 10 102 )) K = ((5.50 X 10 4)/195 X 1 0 2)= ((3.03 X 10 a
K = 155 x 1 0 5 mol dm3 a
4(c)(i)
Ka increases pH decreases More molecules undergo cleavage of the COOH bond
4(c)(ii)
Weak base unsuitable Solution bufered as titration proceeds No suitable indicator
CAPE Chemistry June 2005 U2 P2 QS - Answe Answerr 5(a)(i)
Muscular stimulation due to electrical discharge/muscle tissue contained a conducting fluid.
5(a)(ii)
Named metals eg Zn Zn,, Cu, Ag Electrolyte Lamp or amme ammeter ter
5(a)(iii)
Voltmeter
-
. .
M
N
,-
·�
,
Solution cta g cta g M' (1 mo d 3) 2 5 • c
Sat bdge
u o t u o t N" ·•) 2 'C
5(b)(i)
Ozone is a more powerful oxidizing agent than Cl2 . EG is more positive
5(b)( )(ii) ii)
reaction tion is feasible = 208-156 = + 052 V Net positive value so the reac
5(c)(i)
Cathode: Pb2() +4H·(aq) + 2e Pb2+ + 2H2 (1) Anode: Pb() Pb P b2+ + 2e 2e (2)
5 (c)(ii)
From (1) EG = 147 V From (2) EG = + 013 V E = 147 +013 = 160 V
5 (d)
The useful useful byproduct is water
CAPE Chemistry June 2005 U2 P2 Q6 - Answ Answer er 6(a)) 6(a
In cold alk alkali ali a mixure of hal halide ide (Cl (Cl·) ·) and halate(I) C l are for formed med as Cl21g) + 2NaOH1aq NaC1 N aC11 aq) + NaCO (a (aq q + H20( ) By raising the temperature to 7 °c the rate of disproportionation of C l increases as the halate(V) ions are formed as 3C0·1aq) 2Cl·1 aq + C0•1aq
6(b)
Cl 2, Br2 and 2 react with 20/ to give S40&2 as all giving a net positive E value alu e e.g
EG
values are are> > +.9 V
G
Cl2(aq + 2e· ; 2Cl·1aq) 2S 2032 s S40&2 + 2e· Net
EG =
+36 = -9
EG = EG
+.25 V
However only Cl 2 and Br 2 can react with S20/ to produce 32 because these he se are strong stronger er oxidizing agents more positi positive ve E value tha than n 2. A net negative E is obtained for the 2 . / system so the reaction is not feasible as G
G
2(aq + 2e· s 2 (aq) 20 2 +GOH· 2/+ 3H20 + 4e· E = -4 V 6(c)
AgC white precipitate AgCwhite AgBrcream precipitate Ag yellow precipitate
54 V = -58
EG = EG
CAPE Chemistry June 2005 U2 P2 Q7 - Answ Answer er 7(a)(i)
Water molecules form a complex with the u2 ions. The coordination of the u2• with the water ligand ligandss ca cause usess a split in th thee energies of the d orbitals Electrons in the lower energy orbitals absorb energy in the visible region of the MR The blue colour is the complement of that absor absorbed bed
7(a)(ii)
The 1· 1 · ions displace the H20 molecules in the blue [Cu(H20 )6]2 complex The complex formed [CuCl4] 2 is yellow The green colour is due to a mixure of the blue b lue and yellow complexes
7(b)(i)
Ni
moles= ratio=
N
C
36./587 .65
295/2 246 4
7(b)(ii)
CN
�
CN
34.4/4 246 4
2-
CN � CN 7 (c)(i)
Haemoglobin unit has a central Fe2• ion that coordinates with 0 2 molecules for o r transp transport ort to tissues. The CO molecules form a complex with a higher K , and 02 is displaced s
7(c)(ii)
Using C r20 + 4H•+ Ge· s 2C 2Crr3•+ 7H 20 Mn04 ·+ 8H•+ 5e· s Mn 2 + 4H 20
�= +33 �= +52
C r is readily reduced from + 6 to +3 as indicated indicated by the positive � value value Mn is also readily reduced from +7 to +2
CAPE Chemi Chemistry stry June 2005 U2 P2 Q8 - Ans Answer wer 8(a)(i)
obtained ined from roasting roasting of sulf sulfide ide ores or burning of sulfu sulfurr -50 2 obta 0 2 from ro m air 2502(g) + 02(g) 250 3(g)· Gaseous reactants combine on surface ofV 205 catalyst 50 3 formed absorbed in concentr concentrated ated H2504 -Oleum H25207 diluted to yield H 250 .
•
8(a)(ii)
5 0 2 is an acidic oxide. oxide. Rain becomes becomes acidic due to absorption of acidic gas by water 50 2(g) + H 20 1l H 250 3(aq)·
8( b)(i) b)(i)
CaC031 + 5021g) Ca503l + C021g) CaC03 neutralizes 502 resulting in production of a much weake weakerr acid a cid gas
8( b)(ii) b)(ii)
Volume of 502 present = = m3 = X 3 dm3 At R TP moles 502 = ( 3/24) =47 =47 moles Massof502
=47X64 =267X 267X 3 g = 267 kg
Mass CaC03 required
= (267 (267/64) /64) = 47 kg.
CAPE Chemi Chemistry stry June 2005 U2 P2 Q9 - An Answe swerr 9(a)(i)
-Ozone in the stratosphere offers protection from -Ozone from harmful har mful UV radiation. Exposure can lead to development devel opment of skin cancer and cataracts -Decrease in photosynthetic photosynthetic activity can also occur, occur , decreasing agricul agricultural tural production
9(a)(ii)
Volatile non flammable flammable and chemically inert
9(b)(i)
NH 3 is a pungent gas and an irritant
9(b)(ii)
CCl2 F2 hf - • CCIF2(gl + Cl•(gl (1)
CJ' act actss as a catalyst and can react with more ozone ozone 9(c)(i)
9(c)(ii) 9(c)(ii)
Principle of dynamic equilibrium The concentration of ozone shows no net change The ra rate te of formatio formation n is is equal to the rate of destruction. destruc tion.
CAPE Chemis Chemistry try June 2006 U2 P2 Ql - Answer l(a)(i)
Efect on rate: Rate doubes. Reason: Reaction is 1s ord order er w. r t [H 2(g)].
l(a)(ii)
Efect on rate: Rate x ¼. Reason: Reaction is 2nd order w. w. r t. [NO(g)].
l(a)(iii)
Efectt on rate: Rate x 27 Efec
l(b)(i) Vo.w
Of
•,t > 0o1l•cte 0o1l•cte
l(b)(ii)
Pressure measurement
l(b)(iii)
the appara apparatus tus must be seaed and the voum voume e of gas evov evoved ed mu must st no nott eceed the maimum voume which coud be hed in the syringe used for coecting and measuring the voume of gas
CAPE Chemi Chemistry stry June 2006 2006 U2 P2 Q2 - Ans Answer wer NaCl (aq) + NaCIO (aq) + H20 (l·
2(a)(i)
Cl2(aq) + NaOH (aq)
2(a)(ii)
+7.
2(b)(i)
Reddish brown brown colour colou r
2(b)(ii)
White ppt soluble in NH 3(a (aq q ·
2(b)(iii)
Violet vapour
2(c)
2Br (aq) + Cl 2(aq)
2(d)
Use of fume cupboard cupboa rd
-
-
2Cll (aq) + Br2, 2C
CAPE CAP E Chemistry Chemistry June 2006 U2 P2 Q3 - An Answe swerr 3(a)
Source: air Proces Process: s: fractional distillation.
3 (b )(i)
High pressure
3(b)(ii)
3(c)
Use of a catalyst Decrease the time by lowering the energy required for the reaction
3(d)
Low temperature and hi high gh pressure
3(e)
itmus.. li tmus Red Re d l
CAPE Chemistry June 2006 2006 U2 P2 Q4 - Answ Answer er
4(a)(i)
I f a syst system em in equilibrium is subje subjected cted to a chan change ge processes will occur which will tend to counteract coun teract the change imposed.
4(a)(ii)
Microscopic (molecular scale) processes continue but these are in balance, and, macroscopic properties are constant
4(a)(iii)
KP =
4(a)(iv)
The equilibrium position lies well to the right There is a much greater concentration of products relative relative to reagents
4(b)(i)
Equilibrium position shif to the lef ndothermic reaction favoured according to Le Chatelier's rinciple (to nullify the efect of change Volume of reactants increases and volume of o f product decreases
4(b)((ii)
Equilibrium position shifs to the right. Reduction in volume (reduction in number of moles of gas) favoured Reactant concentration decreases and product concentration increases
4( b)(iii)
No overall efect on position position of equi equilibri librium um The efect on both foard and reverse reactions are the sam same. e.
4(c)
Initial partial pressure of S02 = mole fraction x total pressure = ½ x 5 = 3.333 at 3.3 atm m
(pS03)2 (pS02)2 (P02)
Initial part partial ial pressure of 02 = x 5 = 167 1 67 atm For pS03 to be 3 atm of S02(gl had reacted and 1 5 atm 02(gl had reactedd using mole ratios from reacte fr om equation equation aial pressures of gases at equilibrium: pS02 = 333-3 = 33 atm p02 = 1.67 1.5 = 17 atm KP = (3)2/((33)2(17)) = 9/185 = 486.49 atm
CAPE Chemistry June 2006 U2 P2 QS - Answ Answer er 5(a)
A bufer solution resists pH pH ange on addition of o f small amounts of acid aci d or alkali
5(b)(i)
To maintain a pH of 7.
5( b)(ii)
32 rea reacts cts with excess H· ions and HC03 • reacts with excess OH ions ions
5(c)(i)
Amin o acids contain both acidic and Amino and basic groups. - -H H2 group can ca n react react with excess H· H · ions -OOH group can react with excess ex cess OH ions
5(c)(ii)
Food Foo d processing processing
5(d)(i)
M, of CH C H3COONa COONa= = 82 656/82= 656/82= 8 mol dm3.
5(d)(ii) 5( d)(ii)
K= K = [HJ [CH3 J [ H] = 18 1 2 J so 18 18 15= [HJ 8 and [H] [CH3COOH] .2 8 so [H] = 45 1 mol dm3. Assumption is that the concentration of CH 3C C ions is equal to the concentration of CH C H3 COONa
5(e)(i)
Initial concentration of CH 3COONa= 8 mol dm dm3 Concentration aer adding= 8 + 5 NaOH NaOH= 85 mol dm3 Initial concentration of CH 3COOH COOH= = 2 mol dm Concentration aer adding NaOH= NaOH= 2 - 5 5= = 25 25 mol dm dm3
5(e)(ii)
pH of the new solution does not difer significantly from that of the original solution The ethanoic acid present in the bufer reacts with the OH ions thus decreasing decreasing its concentration
CAPE Chemistry June 2006 U2 P2 Q6 - Ans Answer wer 6(a)(i)
Bonding changes from covalent o ionic. Acid/base character changes from neutral to amphoteric. Character of element changes from non-metal to metal Stability of covalent bonds decreases with increase in atomic radius Basic character increases down the group due to the increase in the ionic nature of the oxide
6(a)(ii)
CC l4 is unreactive with water SiCl4 to PbCl4 are hydrolysed For SiCl4 to CCl PbCl4, d orbitals are available availab le for coordination with water molecules.
6(b)(i)
J: Pb02 . K: PbS04 white precipitate L: 0 2 - relights a glowing splint J is i s an oxidizing agent M: Mn04·(aq) purple colour 0: PbCl2.
6( b)(ii) b)(ii)
P is tin(II) loride/SnCl2 or tin ions P is a reducing agent since it takes orange Cr 2072 to green Cr 3• removes ogen from nitrobenzene and replaces it with hydrogen
6(b)(iii)
The yellow/br yellow/brown own solution of Fe3• goes to green Fe3 + Fe2•
CAPE Chemistry June 2006 U2 P2 Q7 - Answ Answer er 7(a)(i)
A: giant ionic latice. B: simple molecular C: giant covalent/macromolecular D: giant metallic metallic E: simple molecular
7(a)(ii)
A: Al203. 8: S C: Si S i or or Si02• D: Al or Mg. E: PCl5 or PCl 3
7(b)(i)a)
Vigorous reaction with with cold water H2 gas evolved evolve d Alkaline solution formed
7(b)(i)b)
Reacts with steam Reacts slowly at room temperature. Basic oxide formed H2 g a s evolved Burns with bright flame
7(b)(i)c)
Dissolves in wate Acid solution fomed Greenish yellowellow solution formed
7(b)(ii)
CAPE Chemistry June 2006 U2 P2 Q8 - Answ Answer er 8(a)
PVC: electrical insulation. i nsulation. PET: PE T: roofing tiles -C-C and C-CI bonds are strong
8( b)(i) b)(i)
Breakdown of poly polymer mer into monom monomeric eric units units
8(b)(ii)
HCI, NaOH The ester linkages are hydrolysed to release the monomers (acid and alcohol)
8( c)(i)
A n organic solvent solvent eg dichlo dichloromet romethane hane
8( c)(ii)
To increas increase e the surface surfa ce area for action of solvent
8( c)(iii)
Protective eye wear and gas ga s masks.
8(c)(iv)
ndustrial rain coats
8(d)
Reduction in plastic sent to landfills Heat produced from process can be recovered Ash generated still requires disposal. CO2 combustion product contributes to greenhouse efect Chlorinated products of incineration provide health health hazard
CAPE Chemistry June 2006 U2 P2 Q9 - Answ Answer er 9(a)(i)
Difere nt boiling points of comp Diferent componen onents. ts. Fraction richer richer in lower lo wer boiling point components rise up column and collected at the top Fraction richer in higher boiling poin pointt components condenses and ns of of at diferent difer ent levels le vels in in the column column..
9(a)(ii)
Larger alkanes are broken down to smaller alkanes and alkenes suing high temperature emperat ure and/or catalyst soo·c
9(b)
C 10 10H H 22 A23
9(c)
Fractional distillation is necessa to provide useful components for fuel and the petrochemical indust
9(d)
Oil spillage kill bird birds s fishes corals and ruins beaches
9(e)(i)
Cumulative poiso poison n Causes Cause s depression depression
9(e)(iiii))
Incomplete combustion of fuel for CO High temperature empera ture promotes a reaction between N 2 and 2 N 2(gl + 2(gl - N 2(g) ·
9(e)(iii)
Catalytic conveer Electri Electricc cars
CH1 + C2 H4 H4,,
CAPE Chemistry June 2007 U2 P2 Ql - Answe Answerr l(a)(i)
Br2aq) + C2(aq) 2BrCaq)·
l(a)(ii)
K, =
l(b)(i)
=6.9 .90 0 so equiibrium is atained K eq = (0.0546)2/((00389)(00111)) =6
l(b)(ii)
Accurate anaysis of the concentration of the reactants and products and constant environmenta condit conditons ons ie press pressure ure and temper temperature ature
l(b)(iii)
The experiment shoud b e conducted in fume cupbo cupboard ard
l(c)
If the reaction mixure is exposed to a temperature greater than room temperature
[BrC]2 [Br2] [C2]
CAPE Chemist Chemistry ry June 2007 2007 U2 P2 Q2 - Ans Answer wer 2(a)(i)
HCI.
2(a)(ii) 2(a)(iii)
(White) choking fumes of gas.
2(a)(iv) 2(a)(v)
Smell of roten egg/foul smell
2(b)
Increasing polarizability down the group
2(c) Oxidation state change change:: Cl2 0
-
NaCl + NaCO -1 and +
CAPE Chemistry June 2007 U2 P2 Q3 - Answ Answer er 3(a)(i)
Organic phos phosphate phate pesticides.
3(a)( )(iiii))
Green algal bloom.
3(a)(iii)
Eutrophication
3(b)(i)
Concentrations Concent rations are 0 70 70,, 059 and 062 for samples 1, 2 and 3 respectiv resp ectively ely
3( b)( )(iiii))
Average [P043·] = (070 (07 0 +059 + 062)/3 = 191/3 191/ 3 = 064 0 64 mg dm· dm· 3 to 2 sf
3( b)(iii) b)(iii)
limits s [P043 ] is within acceptable limit
CAPE Chemistry June 2007 2007 U2 P2 Q4 - Answ Answer er 4(a)
Bufer solution - regulat regulates es p H b y respon responding ding due due to small additi additions ons of acid o r alk alkali ali
4(b)(i)
H· ions react with anions from fr om the salt salt Conce Concentrati ntration onof H decreased.
4(b 4( b)(ii)
OH ions react with weak aci acid d molecule mol ecules s OH ions neutralized
4(c)(i)a)
Equilibrium shifs to produce H2C03 H2C03 dissociates to increase H concentration in blood.
4( c)(i)b)
Deep rapid breathing clean lungs of C02(g)· quilibrium shifs to the lef to release CO2 from the blood. H· io ions ns reabsorbed re absorbed as equilibriu equilibrium m shifs to the lef
4( d)(i)
K= [H] [CH3 C ] [CH3COOH]
4 (d)(ii)
[H•]= [H•] = Ka [CH3COOH] [H3C] = (175 x 15 x 25)/1 = 44 x 1 mol dm3 pH= pH = log lo g [H [H•] •] pH= log (44 x 15) pH= 44.
CAPE Chemis Chemistry try June 2007 U2 P2 QS - An Answe swerr Using Usin g expts 4 and 5, doubling doubling of [ RX] doubling of rate. proportionalit 1 t orde
1:1 1: 1
5(a)(ii)
Using expts 1 and 2 doubling of [NaOH] doubling of rate proportionalit 1st order
1:1
5(b)
Overall ord order= er= m + n = 2 Rat Rate e equation equatio n = k [R X] [NaOH]
5( c)
Using expt 1
5(a)(i)
s
units dm3 mo·1 s ·1. 5(d)
The mechanism is SN 2.
R
R
"I
HO
_c: X
H.
'H
1�
- ·· C• X / ',
C . .
H
',
+X
'H
5(e)(i)
Higher temperature causes increase in: Average kinetic energ of particles number of collisions with Eac (activ (activation ation energy) and and rate.
5(e)(ii)
Higher concen concentrati tration on results result s in: Number of collisions per pe r unit unit time increases probabilit probabil it of favoura fa vourable ble collision collision increases increases and rate increases increases
5(e)(iii) 5( e)(iii)
Increased suface area results in: Probabilit of favourable collisions increase and and rate increases.
CAPE Chemistry June 2007 U2 P2 Q6 - Answ Answer er 6(a)
Going from top of tab table le to botom: Ionic, ionic, intermediate, covalent, covalent covalent
6( b)(i) b)(i)
Basic
6( b)(ii) b)(ii)
Amphoteric.
6( c)(i) 6( c)(ii) 6( c)(iii) 6(d)
NaOH: pH 13/14. HC: pH 1/2
6(e)
SiCl4 has a simple simple covalent cova lent molecule with weak intermolecular force forces s Si02 has a giant covalent stucture A large number of covalent bonds must be broken to break down the giant latice structure
CAPE Chemistry June 2007 U2 P2 Q7 - Answ Answer er 7(a)
As you go down the group, electrical conductivity increases with increasing metallic character
7(b)(I)
Covalent.
7 (b)(ii)
Covalent.
7(b)(iii)
Intermediate.
7(b)(i v) v)
Intermediate
7(c)
C O2 and Si02 - acidi acidicc (coval (covalent ent struc structure) ture) GeOi Sn0 2 , Pb Pb0 02 Amp Amphot hotei eicc (Intermediate ionic/covalent structures structures))
7(d)
Increase in E values fr from om Ge Pb indicates increase in stability stabi lity of the +2 oxidation state down the group e
E /V
7(e)
S n4• + 2e· 2e· Sn2• +.15 V + Pb + 2e· Pb2 +8 V C 2072 + 14H + e 2Cr3 + 7H 20 +133 V With Sn2 E cell= +33 (+15)= +18 V With Pb2 E ell= + +33 33 {+18) = -47 V e
e
ve value E ,.11 for Pb2 means it will not reduce Cr 2012 +vee val +v value ue E ce for Sn Sn2 suppos th thee reductio red uction n of Cr2012 e
7( f )
Si has available 3d orbitals hile C does not and so CCl does not react with water at er
CAPE Chemistr Chemistry y June 2007 U2 P2 Q8 - Answ Answer er
8(a)(i)
Fractional distillation.
8(a)(ii)
Fractions are separated aording to boiling point Higher boiling point fraction at at the botom of the fractionating column
8( b)(i) b)(i)
N0 is formed from nitrogen and ogen in the air because of high temperatures N l + 20 l - 2N0 · Sulfur Sulfur comes from the fuel fue l itself i tself S!sl + 0 !l - S0 2
2
2
2
2
2
8(b)(ii)
Both N0 and S0 will il l form acid rain Acid rain des destro troys ys buildings and vegetation.
8(c)(i)
Lead is a neurotoxin CO will compete with 0 for haemoglobin
8( c)(ii)
Lead comes from the antiknock agent added to gasoline This forms PbO when burned CO is formed from the incomplete combustion of petrol petrol
8(c)(iii)
Unleaded Unlead ed gasoline is now available on the mark markt t
8(d)
Port/deep harbour facilities Goodd infrastructure eg roads Goo Isolation from residential sites site s Good po�er supply
2
2
2
CAPE Chemistry June 2007 2007 U2 P2 Q9 - Answ Answer er 9(a)(i)
Formation of ozone:
02(g) + h v- O(g) + Og) and
Along with the formation of ozone, degradation also takes place to keep leels constant naturally.
9(a)(ii)
The ozone layer protects the earth from harmful u rays Preents cataracts and skin ski n cancers cancers
9(b)
Causes breathing prob problems lems.. Takess part in the formation of photochemical smog Take smog Destroyss materi Destroy materials als such as rubber Destroys egeta egetation tion
9( c)(i)
Low flammability flammability relatiely unreactie and low boiling point
9( c)(ii)
Refrigerants and foaming agents.
9(d)
They hae long residence times The regeneration of er as it destroys ozone makes it potent
CAPE CAP E Chemistry Chemistry Jun June e 20 2008 08 U2 P2 - Resit Ql Answe Answerr l(a)(i) l(a)(ii)
Nitric acid and concentrated sufuric acid.
l(a)(iii)
Sn and HCI
l(a)(iv) l(a)(v)
B r2(aq)·
l(b)(i)
l(b)(ii)
Cl
and Cl
l(b)(iii)
02
'
Cl
l(c)(i)
Benzene has no substituents so the chorine can go to any position,
l(c)(ii)
The methy group is 2,4 directing so chorine goes to the oho and para positions.
l(c)(iii)
The nitro nitr o group is 3,5 directing so chorine goes to to the meta position
l(d)
Nitrobenzene, benzene methybenzene. The nitro group is deactivating and makes the benzene ring ess reactive The methy group grou p i s activating and makes the the benzene ring more reactive
CAPE CAP E Chemistr Chemistry y Jun June e 20 2008 08 U2 P2 - Resit Q2 Answe Answerr 2(a)
NaHC03 : Ca Can n be obtai obtained ned in high high purity, stable in air and non-hygroscopic. NaOH: hygroscopic
2(b)(i)
H2S04 + 2NaHC03 -> Na2 S04 + 2C02 + H20
2(b)(ii)
From the balanced equation mole ratio of NaHC03 : H 2S04 is 2 : 1 Moles of sulfuric acid used: (6 (6 x 23)/1 23)/1 = 138 mol Moles of NaHC03 needed: needed: 2 x 138 mol = 276 mol Mass of NaHC03 used: 276 x 84 g = 232 g
2(c)
Standardize Standardiz e soluti solution on of NaOH Transfer Transf er aliquot of vinegar to conical flask using pipete Add tw two o or three drops of appropriate indicator to vinegar vin egar Titrate vinegar with NaOH as many many times as needed for accurate results.
CAPE CAP E Chemistr Chemistry y Jun June e 2008 2008 U2 P2 - Resit Q3 Answe Answerr 3(a)(i)
Acid rain formation by burning of fossil fuels, washing with detergents in rivers and and releasee of sewage in in waterways.
3(a)(ii)
Unsafe drinking drinking water and and unsafe water for recreation
3( b)(i) b)(i)
Need increased crop production Increasing population
3(b )(ii) 3(b
Feili zers are Feilizers are leached leache d into the ground wa wate terr Run-of Run-of wate waterr from rainfall rainfall or irrigation irrigatio n enters enter s drain drains s streams river riverss etc Eventual Event ually ly the polluted/contaminat polluted/ contaminated ed water reache reachess the ocean, thus polluting the wat water er
3 ( (c c )
Pb2•: K (aq) yellow ppt pp t (Pb (P b 2)-+ (solub (soluble le in excess HN03). N0 3·: Zn/NaO Zn/NaOH(aq) H(aq) boil -+ gas evolved evolved turns damp red litmus litmu s blue blue (NH3 evolved).
CAPE Chemistry Chemistry June 2008 2008 U2 P2 - Resi Resitt Q4 Q4 Answer 4(a)
Ethanol and Na2C0 3: Ethanol and NaOH:
No reaction. No reaction.
Phenol and Na2C03: Phenol and Na:
No reaction Sodium phenoxide and hydrogen gas gas
thanoic acid an and d Na: Sodium ethanoate an and d hydrogen gas Ethanoic acid and NaOH: NaOH: Sodiu Sodium m ethanoate ethanoate and �vate � vaterr 4(b)
The gien resonance forms of the phenoxide ion sho�v that there is delocalization of the negatie charge on the oxygen into the benzene ring This delocalization increases the ease with �hich a proton is lost from phenols The gien structure of the alkoxide ion sho�vs that there is localization of the negatie charge on the oxygen atom, and this negatie charge is enhanced by the positie inductie efect of the alkyl group to which it is bonded. This increases the tendency of H· ions being bonded to alkoxide ions Therefore phenols show more acidic acidic character charac ter than alcohols
4(c)(i)
Members of a homologous series possess the same functional group and successie members members within a series difer by a fixe f ixed d increment eg -CH2.
4( d)(i)
Structural isomerism refers to compounds possessing the same molecular formula bu butt diferent bonding arrangement or structure
4 (d)(ii)
I
I
I
I
I
I
I
H
O I H
H
H-cC-O- I
H H H I I --
CAPE Chemis Chemistry try June 200 2008 8 U2 P2 - Resit QS Answer 5(a)(i)
2: Ionization chamber, 3: acceleration chamber, 4: (large) magnet 5: ion collector (ion detector).
5(a)(iiii))
To provi provide de high energy electrons to ionize sample
5(b)
RM= ((79 X 50.5) +(81 X 495))/100= 7999 800
5( c)(i)
C "
" C : . "
· "
a
I
157
5(c)(ii) 5(c)(ii)
160- 79B r 81Br
I
158
159
I
160 m/e
161
162
CAPE CAP E Chemistry Chemistry Jun June e 20 2008 08 U2 P2 - Resit Q6 Answe Answerr
6(a)
Potato and barley.
6(b)
Sucrose is conveed to gluco glucose se an andd fructose, then gluc glucose ose is conve converted rted to ethanol and carbon dioxide dioxide using us ing yeast yeast
yeast o r zymase> zymase > 0 II
6(c)
CH CH 0H +[OJ� CH C H +H 0
6(d)
Depression of the central neou neouss system and los losss of inhibitions
6(e)(i)
Job creation wealth creation: exports enhanced technology and fuel production
6(e)(ii)
Education Educati on programme programmess and restricted use
3
2
3
2
CAPE Chemist Chemistry ry June 2009 U2 P2 Ql - Answer l(a)(i)
l(a)(ii)
55 ·c to 60 · c
l(a)(iii)
Sn/HCI.
l(b)(i) I+
H-N-
0
+ 1 -
0
l(b)(ii)a)
Less basic
l(b)(ii)b)
The one pair of nitrogen forms an exended deocaized system sys tem with the deocaized eectrons of the benzene ring This makes the eectrons on nitrogen ess avaiabe for proton acceptance Aso, A so, the ammonium ammon ium ion forms more hydrogen bonds with �ater and is therefore more stabe tha than n the protonated phenyamine
l(c)(i)
l(c)(ii)
Reagents: NaN2 and HCI Condition: temperature of< 5 °.
l(c)(iii)
Soution of sodium hydroxide
l(c)(iv)
Yeow
CAPE Chemi Chemistry stry June 2009 2009 U2 P2 Q2 - Ans Answer wer 2(a)(i)
The stage at which the reactio reaction n is complete or the two solutions hav have e reacted exactly.
2(a)(ii)
The point at which there is a chan change ge in the colour of the indicat indi cator or
2(b)
A known excess of Na2C03 is reacted with BaCl2. The remaining solution of Na2C03 is determined by titration
2(c)(i) 2(c)(ii)
Mole ratio of sodium carbonate to hydrochloric acid is 1: 2 Moles sodium carbonate carbo nate remaining= 4/2= 2
2(c)(iii)
Moles of barium chloride reacted= (5-2)= (5-2)= 3
2(c)(iv)
Concentration barium ions= 3 4 4= = 12 mol dm·3 •
2(d)(i)
25 cm 3 oxalic acid i s placed in a conical flask and 25 cm3 of dilute sulfuric acid is added Mixure in flask heated to approximately 8 °c. The mixure in the flask is titrated immediately with KMn0 4(a q)·
2(d)(ii)
KMn04aq)
CAPE Chemistry June 2009 U2 P2 Q3 - Answ Answer er 3(a)(i)
The conversion of atmo atmosphe spheric ric nitro nitrogen gen to nitrogen compounds.
3( a ) ( i i )
Electrical discharge in the atmosphere (lightning- atmospheric Action of bacteria in plants (legumes)- biological
3(b)
N2!gl + 02!gl- 2N O!g) ·
3( c )
Deforestation and an d power generation (fossil fuels
3(d)
Policies are costly costl y and could result in unemployment
3(e)(i)
Pink.
3(e)(ii)
Concentrated aqueous sodium hydroxide.
3(e)(iii)
Colour: whit white e Appearance: gelatinous precipitate
3(e)(i v) v)
Filtration
CAPE Chemistry June 2009 U2 P2 Q4 - Answ Answer er
4(a)(i)a)
Compounds Compou nds that difer dife r only in the arrangement of atoms in space. in the
4(a)(i)b)
A carbon atom which is bonded to four diferent diferent groups
4(a)(ii)
H
8
ptical isome isomerism rism
O
'N-* �-C -C
a/ "o-B I H-C-H
H
4(a)(iii)
H
H
I • c._ · \
CH3
I
NH2 m or
4(a)(iv)a)
4(a)(iv)b) +
H
I H -' NCC '- /C
n,
I
0
I
H
n
Condensation Condens ation polymerization.
4(b)(ii)
0 ' +
I 'o-n H/ H-C- I
H
4(b)(iii)
o
I
H
4(b)(i)
H
1 ; C H/C I 'o-
0
4(a)(iv)c) + ; H�cc H/C I 'o
Amide
O H 'cc- '-n I / 0
-c-n
I
H
-C-B
CAPE Chemistry June 2009 U2 P2 QS - Answe Answerr 5(a)(i)
Molecules undergo changes in modes of vibration, and absorption of JR radiation occurs when vibrations cause a net change in dipole moment of molecules.
5(a)(ii)
Stretching and bending
5(a)(iii)
Grind sample with an excess of potassium bromide to a fine texure and press this mixure into the for form m of a pellet
5(b)(i)
A: C H B: 0-H and C: C=O
5(b)(ii)
I
/
�0-H
H -C
H 5(c)(i)
o
Advantages: Cheap and uses an environmentally friendly solvent solvent Disadvantage: Yield will be lower
5(c)(ii)
Eficiency is increased due due to increa increased sed suace suace are with increase increased d length of the exr exract actor or
CAPE Chemistry June 2009 U2 P2 Q6 - Answ Answer er 6(a)(i)
Chlorine, Chlorin e, sodium hydroxide and and hydrogen.
6(a)(ii)
At the anode chlorine chl orine ions i ons are conveed to chlorine gas by oxidation:
A t the cathod cathode e �ater is decomposed to give hydr hydroge ogen n by reduction reduction
6(b)
Weed kill killers ers antiseptics and chlorina chlorinated ted organic compounds
6(c)
Function: Sulfur dioxide is a reducing agent It preven prevents ts oxidation of food thereby reta retarding rding food spoilage Disadvantage: Sulfur dioxide distorts the the taste of food
CAPE Chemistry Jun June e 2010 2010 U2 P2 Ql - Answ Answer er l(a)(i)
Hot acidified acidified Mn04•
l(a)(ii) l(b)(i)
CH,
CH,
(b)(ii)
Br
CH
HO
O
l(c)(i)
A macromoecue formed from joining many monomers (sma moecu moecues). es).
l(c)(ii)
Addition.
l(c)(iii)
Poy(ethene)
l(c)(iv)
l(c)(v)
No,, because they do not have >C=C< No
l(d)
HH
,
I
?
N--
I
. 0
R
l(e)) l(e
Simiarity: They both contain the amide inkage
O
11 I
- CC-N N
Diference: The amide inkages are separated by one C atom in proteins, but in nyon 6 66 6 they ar are e separated by b y severa C atoms
CAPE Chemistry June 2010 U2 P2 Q2 - Answ Answer er 2(a)(i)
Radiation consisting of oscillating electric and magnetic fields of energy which can be transmited transmi ted throu through gh space. space.
2(a)(ii)
The distance between be tween successiv successive e peaks of waves of of radiation
2 (a)(iii) (a)(iii)
The number of waves passing a given given point per pe r second secon d
2(b)(i) 2(b)(ii)
95 x 10 7 Hz
2(b)(iii)
Infrared radiation
2(b)(iv)
Radio waves
2(c)(i)
Sample Samp le of Xis accurately weighed weighed on an analytical balance Sample of X weighed is dissolved in a suitable solvent and a standard solution made, using a volumetric flask Sample is filtered to remove re move any solid particles Absorbance of sample solution is measured at a selected wavelength in the U V visib visible le region, region, afer the the spectrophotometer ha had d been blanke blanked d Ensure that sample absorbance does not eceed 1.0 In such a case dilute the sample s ample and re-do the measurement
2(c)(ii)
Ability Abilit y to produce a colour when reacting with analyte Transparent Transp arent in the U V visib visible le region of of the electromagnetic electromagnetic spectrum
2(d)(i) 2(d)(ii)
Emole = E molecule XL= 9.9 X 10·19 J X 602 X 10 23 mol1 = 6 x 10 5 J mo = 600 k mo·1.
1
CAPE Chemi Chemistry stry June 2010 2010 U2 P2 Q3 - Ans Answer wer 3 (a)(i) i) (ii) 3(a)(i
CO2 comes from respiration and N02 from lightning storms.
3(a)(iii) 3 (b )(i )
Electric power generation that relies on burning fossil fuels like coal which can be contaminat contaminated ed with sulfur Burning of gasolin gasoline e in vehicles in heavily populated areas - the there re is ofen incomplete combustion of gasolin gasoline e generation generatio n N O x
3(b)(ii)
Destroys Destro ys aquatic life and leaches soil nutrients
3( c)(i)
nsure container is clean.
3(c)(ii)
Pb2•: K
3(c)(iii)
Pb2·: yellow ppt. N03·: brown ring at junction of con acid and rest re st of solution
CAPE Chemistry June 2010 U2 P2 Q4 - Answe Answerr 4(a)
They have the same molecular formula, CH80, but dierent stuctural formulae- atoms are linked diferen di ferently. tly.
4(b (b))
Alkene and 1° 1° alcohol
4( c)(i)
HHH -6I lI � 6-- =C - O H
4(c)(ii) 4(c)(ii)
3
H
H
Cis isomer:
H
"
I / C fC C C C0H C0 "c=I / � � 1 HCz 2 H C "
z
3
2
3
Trans isomer:
There is i s no asymmetric or chiral carbon therefore no optical isomerism 4(d)(i)
Cracking is the spliting od larger alkane molecules to smaller ones together with the formation of an alkene. This requires requir es high temperature or modera moderate te temperature and a catalyst
4(d)(ii)b)
Bubble each gas separately into brown bromine in an inert solvent The alkane C H10 will hav havee no efect and the alken alkenee C4H8 will immediat immediately ely decolorize it 4
CAPE Chemistry June 2010 2010 U2 P2 QS - Answ Answer er 5(a)
Distinguish between molecules of similar M
r
Prediction of possible identity of simple organc molecule based on fragment frag mentation ation patern. pat ern. Determination of the number of C atoms in the molecule based on M and M+ peaks 5(b 5( b)(i)
M = 78and M+ =79 = 79
5(b)(ii) 5(b
5(b)(iii) The name nam e of the compound is is 2-chloropropane 5(c)
A,(RAM) =((7577 =((7577 /10) x 3497) +((2423/10) +((2423/10) x 3696) =265 =265 +8.95 =3545 =3545
5(d)
Separation of dyes and pesticide analys analysis is
CAPE Chemi Chemistry stry June 2010 2010 U2 P2 Q6 - Ans Answer wer 6(a)
Fractional distillation of liquid air
6( b)(i) b)(i)
Hydrolysis.
6(b)(ii) 6(c)
High pressure favours low volume and low temperature favours foward exothermic reaction
6(d)
The Haber process uses the compromise pressure of 250 atm and moderate temperature of 55 5 5 0 °c with Fe catalyst to increase rate
6(e)
N 3·: So Sour urcce - fer fertil tiliz izers ers Pollu Pollutin ting g bloom/lowers 2 for marine mar ine life
efect efe ct -
Eutr Eu trop ophi hica cati tion on/a /alg lgal al
P43 ·: Sour Sourcece- Detergent Polluting efectefec t- Eutrop Eutrophicati hication/alg on/algal al bloom Pb2·: So Sour urce ce - Car bateries bateries Pol Pollut luting ing efect efect - Carc Carcinoge inogenic, nic, cumulative poson
CAPE Chemistry June 2011 U2 P2 Ql - Answe Answerr l(a)(i)
No responses required.
l(a)(ii)
Test: Add a few drops of acidified potassium permanganate. Obseation: Coour change from pur purpe pe to coouress with A
l(a)(iii)
Obseation: Siver mirror with 8.
l(a)(iv)
Test: Add a few drops of 2,4-DNP Obseation: Yeow/orange precipitate �ith B B
l(b)(i) +
(l)(b)(ii)
Unimoecuar nuceophiic substit substitution ution
l(c)(i)
Step 1: sufuric acid (concentrated) Step 2: sufuric acid (concentrated) and wat water er Step 3: acidified potassium permanganate
l(c)(ii)
Oxidation
Br
CAPE Chemistry June 2011 U2 P2 Q2 - Answ Answer er 2(a)
Accuracy refers to how close a measurement is to the true or accepted value of the quantity being measured. Precision refers to measurements of the same quantity Both accura and precision refer to how closely t\o measurements measurem ents agree with each othe otherr
2(b)
Pipete burete, volumetric volumetric flask fla sk
2(c)(i)
Student 1: 0065, Stud Student ent 2: 115 Student Student 3: 346 Student 4: 0082
2(c)(ii)
Student 1: precise not accurate. Student Student 2: accurate not precise. Student 3: not accurate, not precise. Student 4: accurate and precise
2(d)
Weigh a beaker on an analytical balance. Condition the 10 cm cm3 pipete Fill the pipete pipete to the mark with distilled water room temperat temperature. ure. Transfer Trans fer water from pipete to beaker Weigh beaker beaker and water Record Rec ord \Veight obtained in tab table le of results Repeat steps above until cons consisten istentt mass values values are obtained
CAPE Chemistry June 2011 U2 P2 Q3 - Answ Answer er 3(a)
Heating crude oil, which is a mixure of hydrocarbons, separates components according to volatility. The components are collected by the use of a fractionating tower with the more volatile collected first
3(b)(i)
Breaking up of large large molecules into in to smaller ones
3( b)( )(iiii))
Rearrangement of ato atoms ms in molecules to form new structures str uctures
3(c) 3(d)
In the production of pharmaceuticals, insulators and plastics
3(e)(i)
A and B are yeast yeast and and starch starch
3(e)( )(iiii))
Efeescence would be obseed in the conical flask and a white precipitate would be obseed in the beaker bea ker
3(e)(iii)
The yeast would be killed
CAPE Chemist Chemistry ry June 2011 U2 P2 Q4 - Ans Answer wer 4(a)(i)
Compounds with he same molecular formula but diferent stctural formula.
4(a)(ii)
Chain isomers, eg
I C H
I
I
I
H
H
-C-CC-C-
I
I 7
I
H
c H H
H
Positional Positio nal isomers eg H HH
H-C · ·C C C C O O H H
H HH
H C C C C H H
H HH
H
mole ratio :. X
1
35
20 cm 2
=2
x=y/4=35 y/4=35-2 y/4=1Sand y=6 The molecular formula of the hydrocarbon is isC C2H 6 •
H OH
10 cm3 35cm
CAPE Chemi Chemistry stry June 2011 U2 P2 Q4 - Answ Answer er 4(c)
In order of increasing inc reasing acid strength: alcohols< phen phenols< ols< carboxylic acids. Alcohols are weakest since the alkyl group releases electron density, resulting in a localization of the negative charge on the oxygen oxygen making it less likely to release a proton Phenols are stronger stronger acids than alcohols but still weakly acidic acid ic This is due to the elect electron ron withdrawing efect of the phenyl ring which caus causes es the phenoxide ion to be stabilized by resonance Carboxylate ions are resonance stabilized: e
o I
R
.C0
These ions are less likely to hold on to a proton since the highly electronegative oxygen pulls electron density towards itself and away from the C H bond.
CAPE Chemist Chemistry ry June 2011 2011 U2 P2 QS - An Answe swerr S(a)(i) S(a)(ii)
Electronic absorption between molecular energy levels. --�----- --�----
a•
•
�-
.
S(b)(i)
This is a group of atoms in a molecule responsible for the absorption of electromagnetic radiation
S(b)(ii)
Conjugated system of double bond bondss or benzene structure
S(b)(iii)
Using A= l 12= 288X 1 X C c = 12/(288 x 1) = 42 x 10·3 mol dm·3.
S(c)
The absorbance of standard solutions is obtained A calibration calibration cue of absorbance vs concentration is ploted ploted Using the calibration cuve, the concentration of the unknown solution can be foun found d
5(d) 5( d)
Determinin g the amount of glucose in blood Determining Determining the amount of urea in blood
CAPE Chemistry June 2011 U2 P2 Q6 - Answ Answer er 6(a)
Nitrifying Nitrify ing bacteria, proteins, soil nitrates and nitrogen nitrog en oxid oxides es respectively.
6(b)
Deforestation Defore station and burning of fossil fuels
6(c)
Formation of ozone: Oxygen is dissociated int into o atoms by UV radiation hµ
•
02!gl - O!gl + 0 (gl Ozone is formed by the reaction of oxygen atoms and molecular molecular oxygen
Breakdown of ozone: Ozone decomposes to molecular oxygen and oxygen atoms by lower energy UV radiation
Ozone molecules and oxygen atoms produce two molecules of oxygen
CAPE Chemi Chemistry stry June 2012 U2 P2 Ql - Ans Answer wer l(a)(i)
H H H I I I I H-C-CH-C-C -C--O C--OH H I I I I H H H
l(a)(ii)
butan-1-o l(a)(iii)
H
2-methy propan-1-o
H OH I ---C --H H
H H3H H----
l(a)(iv)
butan-2-o
H H H - - -- H H H
2-methy propan-2-o
l(b) l( b)
Structura Structur a isomerism.
l(c)) l(c
Stereoisomerism (optica (optica). ).
l(d)(i)
butan-1-o
purpe to coouess
l(d)(ii)
2-me 2meth thy y propa pan n-1-o
pur urp pe e to to coo coour ure ess ss..
l(d)(iii)
butan-2-o
purpe purp e to coouress.
l(d)(iv)
2-me 2meth thy y propa pan n-2 -2--o
no co coo our ur ch chan ange ge
l(e)
yeow to green.
CAPE Chemistry June 2012 U2 P2 Q2 - Answ Answer er 2(a)
Forensicc testing. Forensi
2(b)
Obtain a beaker and cover its botom with a solvent (mobile phase). Apply the mixure to be separated se parated as a spot at a short distance from one end of the TLC plate Dip the end of the plate below the spot into the solvent (make sure the solvent sol vent level level does not cover the spot) Allow the solvent to climb the the plate pl ate until it nears the top of the TLC plate plate..
2(c)
Stati ona phase: this is a soli Stationa solid d and is the material which holds the solute on the plate. Mobile phase: this is a liquid and it carries the solute along the stationa phase phas e on the plate.
2(d)
Silica and alumina.
2(e)(i)
For A, A, Rt = (24/68) (24/68) = 035 035 and fo r B, Rt = (51/68 ( 51/68)) = 0 0 75
2(e)(ii)
A is more atracted to the stationa phase and B is more atracted to the mobile phase
2 (e)( )(iii)
Nature of stationa and mobile phases
CAPE Chemi Chemistry stry June 2012 2012 U2 P2 Q3 - Ans Answer wer 3(a)
Reuse newspaper as absorbing material Recycle paper by b y making pa papi pier er mach. Reduce use of paper by using email for communications.
3(b)
Waste streams contam contaminate inate and degrade degrade land, and radioact radioactive ive gases - free radica rad icalsls-relea released sed into ai airr - carcinogenic
3(c)
Carbon dioxide and hydrogen hydrog en sulphide
3( d)(i)
Sucrose is converted to to glucose and then to ethanol by enzymes produce produced d by yeast.
3(d)(ii) 3(d)(ii)
Compound 1: ethanoic acid. Compou Compound nd 2: ethanol ethano l Type of reaction reaction:: oxidation
CAPE Chemistry June 2012 U2 P2 Q4 - Answ Answer er
4(a)(i)
CH
3
I
4(a)(ii)
H
3
I
H C-C - C-H
I
I
I
3
I
Br Br
OH Br 4(a)(iii)
I
H C-C-C-H
3
I
CH H
CH
H
I
I
CH \ C=O + H 0 + CO
I
I
CH
3
4(a)(iv)
3
I
H C-C - C-H 3
2
O H OH
2
3
4(b)
es not . It doe It do
4(c)
Both groups atached to each carbon of the double bond are the same, and there are no common groups atached to the carbon atoms of the double bond.
4(d)
B HC H \ I C=C + \ I H HC
HC
3
3
H -B r �
3
4(e)
Electrophilic addition
H
Br
H
I I I \0 - C-H � H C-C - C-H I I I I 3
HC 3
H
CH
3
H
CAPE Chemistry June 2012 U2 P2 QS - Answe Answerr 5(a)
Figure 2 is a sintered glass cucible used for filtration by suction and dying of precipitate in oven. Figure 3 is a suction funnel and is used for filtration by suction
5(b)(i)
Partition coeficient (r)
5(b 5( b)(ii)
1 Temperatur Temperature e 2 Solute does not react with solvents
5(b)(iii)
Organic compounds are generally more soluble in non polar solvents that in polar solvents like water Solvents are immiscible An organic compound is paitioned between two solvents by shaking and the organic compound is recovered recovere d by distilling of the solven solventt afer separation of two layers
5(b)(iv)
Concentration Concentratio n of Yin water water= = (16/10 (16 /100 0= 0016 Concentratio Concent ration n of Yin ether= (84/ (84/200) 200)= = 0042
concentration of of ester este r in in toluene tol uene concentration of ester in water
Partition coeficient = (0042/0.016) = 2625 with respect to K, ether and water
CAPE Chemi Chemistry stry June 2012 2012 U2 P2 Q6 - Ans Answer wer 6(a)
Expansion possibilities, political situation, readily accessible energy need needss and good transportat transportation. ion.
6(b)
One safety concern is that it is a high pressure process and there is the possibility of explosions The safety measure for this concern is that workers should be fully aware of evacuation procedures Another safety concern is that spil spilll of product is likely in transportio transportion n The safety measure for this concern is that clea clean n up measures should be developed
6(c)
2CO + 02- 2C02 and 2CO + 2NO- 2C02 N2.
6(d)(i) 6(d)(ii)
Production of smog; adverse efects on respiratory system
CAPE CA PE Chemistry Chemistry Jun June e 2013 U2 P2 Ql - Answe Answerr l(a)(i)
and
H
I
I
I
I
H
H
-C-C-C-
1
+
R'-C0 N
OOHO l(a)(ii)
I
and
I
-C-CC
I
I
Cl3 - C- R
OOHO l(a)(iii)a)
Saponification.
l(a)(iii)b)
Transesterification.
l(a)(iv)a)
Soap making
l(a)(iv)b)
As fue (biodi (biodiese. ese.
l(b)(i)a)
Orange precipitate produced.
l(b)(i)b)
KMn04 decoourised.
l(b)(i)c)
Z is an adehyd adehyde e
l(b)(i)d)
Z is an a n aromatic adehyde
l(b)(ii)
c,
I
0
I
�
H
.
l(c)
I 0 + C = O + r - C-0 H J /� "
�
.G
CN
I -C-o I CN
CAPE Chemistry June 2013 U2 P2 Q2 - Answ Answer er 2(a)
Bending and stretchi stretching ng vibrat vibrations. ions.
2(b)
Laborato identification of org organi anicc compound compoundss and identification of functional groups.
2(c)(i)a)
Acetone.
2(c)(i)b)
The >C=O at a wavenumber wavenum ber of 1715 cm·1.
2(c)(ii)a)
2-propanol
2(c)(ii)b)
-OH at a wavenumber of 3350 cm cm··1.
2(c)(iii)a)
Butanoic acid
2(c)(iiib
>C =O at a wavenumber 1710 cm· cm·1 an and d -H at a wavenumber of 3400 cm cm··1
2(d)(i)) 2(d)(i
Grind the solid sample with potass potassium ium bromide and for form m this mixure into a pellet under pressure Insert the sample into machine and record rec ord readings
2(d)(ii)
NaCl i s transparen transparentt to infrared radiation
CAPE Chemistry June 2013 U2 P2 Q3 - Answ Answer er 3(a)(i)
Leaching.
3(a)(ii)
Fungicides and herbicides
3(b)(i)
Reagents: FeS04(aq); concentrated H2S04
•
Obseations: A brown ring forms at the interface of the two liquids 3(b)(ii) 3(b
Reagents:: Ammonium molybdate Reagents Obseations: Yellow precipitate
3( c)(i)
Difusing from atmospher atmosphere e and aeration from rapid movement
)(iiii)) 3( c)(
Ecessive nutrients (N0 3• and Pol·) lead to algal growth followed by bacterial decom decomposit position ion on o n death (remov (removal al of oxygen)
3(c)(iii)
It cause causess corrosion corrosio n in boiler pipes pip es due to acidity aci dity due to the presence of CO2.
3(d)
Filtration and chlorination
CAPE CAP E Chemistry June 2013 U2 P2 Q4 - Answ Answer er 4(a)(i)
NaOH
4(a)(ii)
Br
Br
B 4(a)(iii)
11
Cl - C - CH 2 C 3
4(b)(i)
Step I: concentated sulfuic acid and concentated nitic acid. Step II: 2 and Fe . Step 11I: 11I: Sn and concentated concentat ed HC 3
4(b)(ii)
4(b)(iii)
Electophilic substitution
4(b)(iv)
N0 2 i s a me meta ta diecto and theefoe diects the incoming substituen substituentt to the meta position.
4( c)(i)
Nitobenzene, benzene methylbenzene.
CAPE Chemistry June 2013 U2 P2 Q4 - Answe Answerr 4(c)(ii)
l
Cl
Cl
CAPE Chemistry June 2013 U2 P2 QS - Answ Answer er 5(a)
The ratio of the solute concentrations immersed in solvents at a given temperature.
5(b)
Using the the formula k= C,.Jche :. (0854/10)/(0159/10) = k= 536 (0854/10)/(0159/10)= Let the mass of acid in water= x g (x/10)/((1-x)/20)= (x/10)/((1-x)/20) = 5.36 736 736 x 5.36 = 536/7 .36 .36= = 0 0728 728 g
X
5(c)(i)
Steam distillation.
5((c)( 5 )(ii) ii)
Solvent exraction
5(c)(iii) 5(c)(iii)
Fractional distillation.
5((c)(i v) 5 v)
Simple distillation distillation
5((d) 5
Liquid of composition x when heated, produces a vapour of composition a1 Vapour on condensing produces a liqu liquid id of composition x1 Liquid has greater concentration of A than B Repeated vaporization and and condensation produces liquid liquid A which is the distillate .
CAPE Chemistry June 2013 U2 P2 Q6 - Answ Answer er 6(a)
The ore is crushed and treat treated ed with sodium hydr hydroxid oxide. e. The filt filtrate rate is seeded to produce Al(OH The Al(OH is heated to produce aluminium oxide
NaAl(OH)4(aq) -> NaOH (aq) +Al(OH!s)· 6( b)(i) b)(i)
Red mud
6( b)(ii) b)(ii)
Harms flora and fauna, and disfigu disfigures res the environment
6( c)(i)
Anode reacti reaction: on: 202 -> 02(gl + 4e- Cathode reaction: Al3 +3e-> Al ii)) •
6(c)(ii)a)
The process requi requires res a large quantity of energy
6(c)(ii)b)
Energy demand demandss and pollution efects are reduce reduced d
CAPE Chemistry June 2014 2014 U2 P2 Ql - Answ Answer er l(a)(i)
To break the bonds in Br B r2 moecues and produce bromine radicas.
l(a)(ii)
l(b)(i)
K b = [RNH/] [OH·] [RNH 2]
l(b)(ii)
Ethyamine is the stronger stronge r base
l(b)(iii)
The ethy group increases the avaiabiity of the one pai pairr of eectrons. I n phenyamine phenyamine,, the nitrogen nitrog en atom's one pair of eectrons i s deocaized deocaized int into o the benzene ring, decreasing their avaiabiity
l(c)(i)
t i s arg arger er than 93 938 8
l(c)(ii)
The avaiabiity of nitrogen's one pair of eectrons is further reduced due to the presence of-ON system
l(d)(i)
Vigorous react reaction ion and the evoution of dense white fumes. fum es.
l(d)(ii)
Pae yeow yeow precipitate precipitate formed
l(d)(iii)
White precipitate produced
l(d)(iv)
B r2 i s decoourize rized d
CAPE Chemi Chemistry stry June 2014 U2 P2 Q2 - Answ Answer er Vsible
2(a)(i)
raditon
Incc reasing frequency In 2(a)(ii)
Infrar Inf rared: ed: Ban Band d X ray rays: s: A.
2(b)
C=
=
V 30 x 108= 45 x 101 5 '
'= (30 x 1 08)/(45 x 1015)= 67 x 10·8 m 2(c)
S2 in wines/juice
2(d)(i)
Step 1: To produce S from miure Step 4: To ensure the removal of all traces of wat water er
2(d)(ii)
Suction flask and suction funnel
2(d)(iii)
Oven.
2(e)
Mass of washing washing sod soda= a= 64 644 4 g Mass of anhydrous sodium sulfate= (3709-34 (3709-3425 25)) g= g= 284 g Mass of water= (644-284) g = 360 g (2.84/142) moles of Na2S4 combined with (360/18) (360/18) mo moll of water =
1 mole
= 1 0 moles H
:.
(360/18) X (142/284) = 10
CAPE Chemistry June 2014 2014 U2 P2 Q3 - Answ Answer er 3(a)(i) 3(a)(ii)
Temp: 400 °c- 500 °c. Pres Pres:: 25 atm -200 - 200 atm.
3(a)(iii)
Fractional Fract ional distillat distillation ion of air
3(a)(iv)
Closeness to labour labou r force force Closeness to water source
3( b)(i)
The process is exothermic An in temp will shif eq'm to lef resulting in a decrease in yield of ammonia
3(b)(ii)
Foard rxn favours an inease in pressure due to lowering of the total number of molecules. Eq'm Eq' m shifs to to right right This increases yield of ammon ammonia ia
3(c)(i)
A: steam reforming B: dissolving of of CO2 in water C: condensation
3(c)(ii)
Fe catalyst (finel (finelyy divide divided) d)
3(c)(iii)
Liquid
CAPE Chemistry June 2014 U2 P2 Q4 - Answe Answerr 4(a)
Primay: one ethyl group atached to the carbon atom bonded to the halogen. Seconday: two alkyl groups atached to the carbon atom bonded to the halogen Teia: three alkyl groups atached to the carbon atom bonded to the halogen
4(b)(i)
2-bromobutane.
4(b)(ii)
T he presence of a chira chirall centre results in optical isomer isomerism. ism.
4(b)(iii)
4( c)(i) 4(c)(ii)
2-bromo-2-methylpentane
C C
H.iC
I . c+ l�
' \CrBr
H3C' �.
I- l C1
3
C
a
C+�Ol Ol
i�
f;C J-
+
3
l C 3
\
C ()1 C ()1
H3C'# '#J J HC 3
4( d)(i)
O f white precipitate produce produced d
4(d)(ii)
NaN0 N03aq) +AgBr(s) NaBr(aq) + AgN03aq) -> Na
CAPE Chemistry June 2014 U2 P2 QS - Answe Answerr 5(a)(i)
Electron beam beam knocks kn ocks of e- fro from m molecule molecule producing positive ions
5(a)( )(iiii))
Magnetic field separates ions according to their respective m/z ratios for detection.
5(a)(iii)
The recorder presents ions as a series of peaks according to their respective ion curr currents ents produced
5(b)
the ratio of the relative abundance of the M/(M+) (molecul (molecular ar ion ion)) peaks indicates the number of carbon atoms in the compound compou nd
5( c)(i)
88
5(c)(ii)
43
5(c)(iii)
H
O
H
I
II
I
H-CC0CCH
H
5(d) H
I
I
I
H
H
,
H-c-
H
O
H
I
" o cH
CAPE Chemistry June 2014 2014 U2 P2 Q6 - Answ Answer er 6(a)(i)
Uv radiation breaks down down ozone into into O radicals and oxygen molecules. molecules.
The ozone and oxygen atoms react to give 0 2 molecules
6(a)(ii)
CFC's
6(a)(iii)
Cataracts and skin cancer
6( b)(i) b)(i)
Yeast contains the enzyme zymase zymase whi which ch catalyses the breakdo�n of gluco glucose se into ethanol and carbon dioxide C 6H1206 2C2H50H + 2C02• -
6( b)(ii) b)(ii)
Fractional distillation
6(c)
Yes becau because se the sale of beverages bevera gesgives revenue and job opportuniti opportunities es
CAPE Chemistry June 2015 U2 P2 Ql - Answe Answerr l(a)(i)
Therma cracking.
l(a)(ii)
Temp Te mperatures eratures in excess of 60 600 0 °c.
l(a)(iii)
8: CH4 C: CH3CH =CH2
l(b)(i)
The 2s eectrons are unpaired and one one of these is promoted to the th e empty 2p orbita The 2s and three 2p orbitas are hybridized to give four equivaent s p3 hybrid orbitas
l(b)(ii)
Aqueous bromine with propane in sunight
-
H
I
-
2ar
-
I
-
" ., ' !
-
H
H
H
C
-
C
-c
'
I
I
"I
H-c-e-d. I
I
c--e-H
I
.,
.
.,
� �) H - - C - - B, - ! - - r
" -
H
----- c-c-
H
l(b)(iii)
Free radica substitution
l(c)(i)
Red brown coour of bromine is decoorized decoorized
l(c)(ii)
Purpe coour of permanganate is decoorized
CAPE CAP E Chemistry Chemistry June 2015 U2 P2 Q2 - Ans Answer wer 2(a)(i)
Reading burete at eye level increases accuracy.
2(a)(ii)
Adding titrant dropwise close close to the end point increases accuracy
2(b)
Large molar mass and high degree of purity
2(c)(i)
II J
·t
f
H '
�
+
32 �
1.
.
-
I
•
'
i
r
'
30
10
IS
20
25
Volume rci (')
JO
5
40
"4 5
CAPE Chemistry June 2015 2015 U2 P2 Q2 - Ans Answer wer 2(c)(ii)
24.5
2(c)(iii)
25 cm3 NaOH contain cont ain (20 x 25)/1000 = 005 005 mol Mole ratio r atio of HCI to NaOH Na OH is is 1: 1 so moles HCI = 005 0 05 245 cm 3 of HCI contain 005 mol HCI and 1000 cm3 contai contain n (005 x 1000)/245 1000)/245 = 204 moles HCI H CI [HCl(aq)] = 2.04 2.04 mol mo l dm·3.
2(d)
Pipete 25 cm3 sodium hydroide solution into a polysty polystyrene rene cup Allow solution to sta stand nd for a fe�v minutes minutes and measure it itss temperature HCI added from burete in 5 cm3 portions rom burete The miure is stirred and the temperature recorded This is repeated until 45 cm3 of acid hae been added
CAPE Chemistry June 2015 U2 P2 Q3 - Answ Answer er 3(a)
Increased pressure of reagen, decreased temperature and the use of a catalyst.
3(b)(i)
If one o r more factors which afect an equilibrium system, the position of the equilibrium shifs in the direction which opp oppose osess the change.
3(b )(ii) 3(b
Low temperature and high hig h pressure press ure
3(b )(iii) 3(b
S 0 3 is dissolved in concentrated H 2S04 to produce oleum Oleum is diluted with water to yield concentrated H 2S04 •
3(b)(iv) 3(b)(v)
H2S04 can cause blindness if it gets into eyes, H 2S04 can cause burns to the skin and flesh, and the reaction between sulfur trioxide and water is highly exothermic
CAPE Chemi Chemistry stry June 2015 U2 P2 Q4 - Answe Answerr 4(a)
The process of linking linking one type of monomer monomer with wi th double double or triple bonds to yield the poly polymer mer which is the only product of the reaction (addition polymerization). polymerizat ion). The process of linking linking two types t ypes of monomers monomers to give both bot h the th e polymer an and d a small smal l molecule molecule (condensation polymerization)
4(b)
Polysaccharides eg starch, and proteins
4(c)
' ' . ' H
1
( HO - C •
+
-
b%le •I,& dtco\Q�( dtco\Q�( 0W 1 / H2o
0 H
4(d)
I I The link between the two monomers is -CN.
The remaining pas of the repeating unit are
H
H, I 0 , '
I C
and
" /
I
#o
N-C-C
\
H
So the monomers are
I ,0 , ' I 3 O
and
3
CAPE Chemistry June 2015 U2 P2 QS - Answ Answer er 5(a)
Chromatography Chromatog raphy involv involves es the sepa separatio ration n of compo components nents of a mixure between two phases ie. the paitioning of the components of the mixure between betwe en a stationa phase and a mobile phase Partitioning results because the mixure's componen experience diferent absorptio absorption n force forcess with the stationa phase and have have diferent solubilit solubilityy with wi th the mobile phase
5(b)(i)
By the use of a reagent called a visualizing agent or a locating agent This reacts with the componen componentt and forms a coloured compou compound nd
5(b)(ii) b)(ii)
Using R f = distance travelled by solute/distance solute/distance travelled b y sol solven vent, t, forr Q , R f = 25/135 = 02 and for R, R f = 125/135 = 09 fo
5(b)(iii) b)(iii)
Q is more polar so it is more strongly adsorbed onto the stationa phase than R which is not as polar as Q
5(c)
TLC can separate small amounts of compounds and is used to separate amino acids Column chromatography is used where large amounts of substances need to be separated and collected Fractions from column chromatography can be collected collected for analysis
CAPE CAP E Chemistry Chemistry June 2015 U2 P2 Q6 - Answe Answerr 6(a)
Hydrogen
Chlorine
0 -
t
Concentratd sdium hld
/ Titanium anode
" Steel cathode Dapagm
l
Sodium hydroxide hydroxide solution soluti on contaminated with NaCl.
Anode reaction: 21·(aq)-2e-> Cl21gl Cathode reaction: 2H(aq) + 2e·-> H2(g)· 6(b)
The use of the asbestos diaphragm is of concern since asbe asbestos stos is consi considere deredd to be a carcinogen and dy as asbes bestos tos fibre fibress can be inhaled, causin causingg respirato problems.
6( c)(i)
CFC's accelerate the depletion of the ozone layer in the atmosphere Destruction of the ozone layer allows hamful ultraviolet radiation to reach the suace of the earth earth CFC's are broken down in the stratosphere to produce chlorine free radicals which react with ozone causing its conversion to oxygen oxyg en
6( c)(ii)
Carbon dioxide is a product of combustion of fossil fuels and it is a greenhouse gas Increased concentrations of carbon dioxide contributes to the greenhouse green house efect ie globa globall warming This has h as a negative efect on the atmosphere through melti melting ng of glaciers and ice caps increase in sea levels levels
CAPE Chemistry June 2016 U2 P2 Ql - Answ Answer er l(a)
Typ e of isomerism in which compound have the same moecuar formua but Type diferentt structur diferen structura a formuae.
l(b)(i)
Voume of carbon dioxid dioxide e produced = 30 cm3 Voume of oxygen consumed = 50 cm3 One moe of hydrocarbon therefore produces 3 moes of CO2. Therefore Therefo re x = 3, in x + (y/4) Using voume of oxygen consumed x + (y/4) = 5 which giv gives es y = 8 Formua Formu a of Xis C H8 .
l(b)(ii)
Dispayed formua:
H H l
I
-CC- I I H
l(c)(i)
H
H
-
C
-
C
-
H
H
H
C
-
H
H
C
-
0
H
-
C
-
C
-
0
H
-
C
-
H
2-methy propan1o
/
/c=,
H
H
H3C H3 C ,
-
l(c)(ii)
C
c i sb sb u t2 t2 ene
2methy propano propano
H3C,
/H
H
3
rab ra b u t ne
CAPE CAP E Chemistry Jun June e 2016 2016 U2 P2 Ql - Answe Answerr l(d)
First pair pair of compounds: compounds : Test:
To bot both h comounds, add add alkaline iodine solution.
Obseation:
Fine yellow cstals cstal s roduced with with the first comound como und No change seen with the other
Second pair of compounds: Test:
To bot both h comounds add a few dros of acidified otassium ermanganate
Obseation:
Potassium ermanganate goes from urle to Potassium colourless with the first comound No change obseed with the other
CAPE Chemistry June 2016 U2 P2 Q2 - Answ Answer er 2(a)
Compounds have natural modes of vibratio Compounds vibration. n. Absorption of JR ours when the freque frequency ncy of the radiation equals the natur natural al freq frequen uency cy of the compound
2(b)
The compounds must undergo a change 1n dipole on abso absorptio rption n of JR radiation
2(c)(i)
3350-3500 33503500 cm·1 = NH 2 and 680-800 680-800 cm1 = >C =O
2(c)(ii)
Name: aminoethanoic acid
2(c)(ii)
Displayed formula:
H , 7 f N-C '
HI
\
0
2(d)
Finely Fine ly gro ground und mixture of the compound and NaCl i s press pressed ed into a tablet
2(e)
Cannot be used fo forr nonpolar compou compounds nds
CAPE Chemistry June 2016 U2 P2 Q3 - Answ Answer er
3(b)
Fertilizers leached Fertilizers indust.
into int o ground water and mercu mercu fro from m the c hl hlor or alkali
3( c)(i)
Radioactive waste wast e causes cancer and lead causes poisoning poisoning
3(c)(iiii))
Washing with phosphate phosphate detergents and feilizers can cause eutrophition and limit oxygen content
3( d)(i)
Pb2 test: add dilute hydrochloric acid Pb 2 obseation: white precipitate •
N0 3• test: add FeS04 follo�ed by concentrated H2S04 slowly N0 • obseation: brown ring 3(d)(ii)
Pb2·(aql + Cl·(a P (s)· · (aq ql -> bCl 2(s)
CAPE Chemistry June 2016 U2 P2 Q4 - Answe Answerr
4(a)
Reaction I Electrophilic substitution. Reaction JV: Diazotization
4(b)
Reactionn Reagents Reactio Reagents - conc concentr entrae aedd H S0 and HN0 Condition emperature of 55 ·c to 60 ·c. 2
4
3
.
Reaction IV: Reagents-Na Reagents-Na00 and HCl · Conditions-temperature of 2
aq)
(aq)
-5 ·c
4(c) 4(d)
QN=
c1-
3
3 '
3 ' /
Br
+
4(e)(i)
Br
HO
Br H Br -ABr
0
Br
4(e)(ii)
O +
a
'
B
4(f)
o
� 9 1 � '1
3•
+
Br 4(e)(iii)
, I
3
CAPE Chemistry June 2016 U2 P2 QS - Answe Answerr S(a)(i) S(a)(ii)
Mixing occurs with zero heat change and zero volume change.
S(b)(i)
A consta constant nt boiling mixure mixure
S(b)(ii)
The compositio composition n of azeotropes changes with pressure
S(b)(iii) 8.pt
B.pt
"\
M
z
X
10
Comositn
Liquid of composition X boils at temperature T1 Vapour has higher composition of A As distillation continues, vapour produces azeoope M. The temperature of o f the residue ri rise sess producing pure B .
S(c)
Mass of compound in organic solvent= x g Mass of compound compound in water= (5-x) ( 5-x) g. Concentration of o f compound in water Concentrati Concen tration on of o f compound compound in ether
(x/25)/((5-x)/100)= = 28 g. = 1/0200 = (x/25)/((5-x)/100)
CAPE Chemistry June 2016 U2 P2 Q6 - Answ Answer er 6(a)(i)
Colite and aluminium fluoride are added to alumina to lower the melting point The cell is lined with carbon which is the cathode. The carbon anode dips into the molten electrolyte Anode reaction: 202 1, 02(gl + 4e· Cathode re reaact ction:Al ion:Al 3 1, 3e· 3e · Al (s (s)) •
6(a)(ii)
Oxygen produced reacts with the carbon anode to produce pro duce carbon dioxide
6(a)(iii) 6(b)
Availabil ity of energy - source of electrical power Availability power transpo transpoation/us ation/usee of railroad railr oad seice seicess and appropriate disposal of toxic waste.
6( c)(i)
Processing materials which would otheise become waste
6( c)(ii)
Aluminium is shredded and hot air Aluminium a ir blown on shreds to remove remo ve coatings The shreds are melted to molten aluminium which is made into in to blocks
6(c)(iii)
Mirror reflectors reflectors in alloysalloys- for aircrafs/cars aircrafs/cars electrical cables
CAPE Chemistry June 2016 U2 P2 Q6 - Answ Answer er 6(a)(i)
Colite and aluminium fluoride are added to alumina to lower the melting point The cell is lined with carbon which is the cathode. The carbon anode dips into the molten electrolyte Anode reaction: 202 1, 02(gl + 4e· Cathode re reaact ction:Al ion:Al 3 1, 3e· 3e · Al (s (s)) •
6(a)(ii)
Oxygen produced reacts with the carbon anode to produce pro duce carbon dioxide
6(a)(iii) 6(b)
Availabil ity of energy - source of electrical power Availability power transpo transpoation/us ation/usee of railroad railr oad seice seicess and appropriate disposal of toxic waste.
6( c)(i)
Processing materials which would otheise become waste
6( c)(ii)
Aluminium is shredded and hot air Aluminium a ir blown on shreds to remove remo ve coatings The shreds are melted to molten aluminium which is made into in to blocks
6(c)(iii)
Mirror reflectors reflectors in alloysalloys- for aircrafs/cars aircrafs/cars electrical cables
CAPE Chemist Chemistry ry June 2017 2017 U2 P2 Ql - Ans Answer wer l(a) l( a)
1. A A members contai contain n the sam same e func function tiona a group 2 A A member can be represented by by a genera formua 3. Physica propeties propeties of members va with increa increasing sing number of carbon atoms
l(b)(i)
C
H
0
Mass/g
0.40
0.06
054
Moes
003
006
003
Simpest Simp est ra rati tio o
1
2
1
So empirica formua is C H20 l(b)(ii)
C2H402,
l(c)(i)
CnH 2 n•COOH
l(c)(ii)
II
H, c, 0 I Cl
l(d)
The pK vaue of A wi be arger since the chorine atom of the substituted acid wit withdr hdraw awss ee eectro ctron n density from from the 0-H bond making H · more easiy ost
l(e)(i)
Add akaine iodine soution to each compound and wam The first compound shows no visibe change whie the second produces yeow cstas
l(e)(ii)
Add a few drops of bromine to each The first mpound shows no change whie hi e the seco second nd causes the red coour coou r of bromine bro mine to disappear
0
CAPE Chemistry June 2017 U2 P2 Q2 - Answ Answer er 2(a)(i)
The degree to which a measure measurement ment is close to the true value. value.
2(a)(ii)
The degree to which measurements are close to each oth other er
2(b)
Steam distillation
2(c)(i)
C , G H.
2(c)(ii)
B , E.
2(d)(i)
C a •(aq) + (204
2(d)(ii)
Molar mass of calcium oxalate= 128 g mo·1
2
2
(a
q)- CaC 204(s)
Moles of calcium oxalate precipitated= (619/128 (619/128)) mol mol= = 48 mol Therefore moles moles of calc calcium= ium= 48 mol Mass of calcium calcium= = (484 (484) )g= g= 193 g Percentage calcium calciu m in sample= (193 (193/496 /496 1% 1%= = 39%
CAPE Chemistry June 2017 U2 P2 Q3 - Answe Answerr 3(a)(i)
3(a)(ii)
It abso absorbs rbs ultraviolet radiation, preventing prev enting damaging da maging radiation fro from m reaching Earth's surface. hf
02(g)- O(g) "g) g) + 0g) + Mg 03g
M'g;
ozne
3(b)(i)
3(b)(ii)
3 ( c)
1. Respi Respirato rato illnes illnesss can result. 2 Reduced crop yield and fo fores restt growth. hf
N02·(g)- O O
No 1 Test: Add aqueous sodium sodium hydroxide and zinc metal and warm Inference: Nitrate Nitrat e ion present No 2 Inference: lead() lead() ion present No 3 Inference: cyanide cyani de ion pres present ent
CAPE Chemistry June 2017 U2 P2 Q4 - Answe Answerr 4(a)
coh hol: a alco Prim Pr ima H
I
-C
C O
I
H
An alcohol in which the -H group is bonded to a carbon atom which is bonded to only one other carbon atom. Seconda alcohol: H
H
O
I I C -C - H -C -C C C I I
An alcohol in which the -H group is bonded to a carbon atom which is bonded to tvo other othe r carbon carbo n atoms Teia alcohol: 3 I I CCC I I
An alcohol in which the -H group is bonded to a carbon atom which is bonded to to three thr ee other oth er carbon carbo n atoms. 4(b)(i)
Type Ty pe of reaction: reaction: dehydration. dehydration. Structural Structu ral formula of compound D:
(b)(ii)
=C2
0
Eis formed by the oxidatio ox idation n of a seconda alcohol to a ketone ket one Fis forme formed d by the oxidation of a prim prima a alcohol to an aldehyde.
CAPE Chemistry June 2017 U2 P2 Q4 - Answer 4( c)(i)
E:
4 (c)(ii)
A:
0
F:
B:
OH
4(d)
A will rotate plane polarized light; B will not.
CAPE Chemistry June 2017 U2 P2 QS - Answ Answer er 5(a)(i)
Stable in air at room temperature, available in a state of high purity and has a large relative formula form ula mass.
5(a)(ii)
It is not considered a primary standard because it absorbs water from the atmosphere and dissolves in it.
5(b)
From A to B there is a consistent temperature rise as HC0 3·(aq) and H*aq) ions react. When all the HC0 3(aq) ions have reacted with H*(aq) ions the highest temperature is reach reached ed at B. As cess H*(aq) ions are added the temperature decreases from B to C
5(c)(i)
Moles of carbonate used = 25 x 25 x 1 = 625
5(c)(ii)
Moles of acid reacted= 5 5 x 25 x 25 x 13= 3125
5(c)(iii) 5( c)(iii)
Concentration of acid= 3125/ 3125/2 2 =16 mol dm· dm·
5(d)
Potentiometric titration
5(e)
Emf measu measuremen rements. ts.
3
3
.
CAPE Chemistry June 2017 U2 P2 Q6 - Answ Answer er 6(a)(i)
The decomposition of large hydrocarbon molecules into molecules with smaller numbers numbe rs of carbon atom atoms. s.
6(a)(ii)
The conversion of straight chained or unbranched alkanes into branched chained and aromatic hydrocarbons
6(b)
N2(g) + Hg) ; 2NH3(g) H = -ve High pressure favours reduction in the number of molecules and therefore the forward reaction which produces ammonia Low temperature favours the foward reaction since the foward reaction is exothermic
6(c)
Act uall pressures used are between 200 and 10 atmos Actua atmosphere pheres. s. Act Actua uall compromise temperature of 500 °C is used At low temperatures the rate of achieving equilibrium (rate of production of ammonia) is slow. An iron catalyst is is used u sed to to increase the rate.
6(d)
Ammonia base ferti Ammonia fertilizer lizerss are leached into gr groun ound d water This leads to overgrowth of algae alga e leading to eutrophication
CAPE Chemistry June 2018 U2 P2 Ql - Answe Answerr
l(a) l(b)(i)
B: eectrophiic addition. C: nuceophi ophiic substitution r
i
H H1- I , - -c
l(b)(ii)
I
I
CH3 1 I
I
I
-c-c--c--1 I
I
I
I
O
M
l(c)
C I / C-- I \"c �2 H
H3
+
H3
H
H
C I I C CI CI C C H
,>
H3
H2
H3
H Br
Br·
- Namee of test: oxidation Reagent: acidified potassium pemanganate Nam Obseations: yeowbrown Structure of expected coour of bromine fades or product: disappears, white precipitate is produced and an antiseptic 0 sme is noted Structure of expected With NaO : product: H
l(d) l(d) l(e)
H3
Br
Br
HO
a
H
w
O Na• "
CAPE Chemistry June 2018 U2 P2 Q2 - Answ Answer er 2(a)
Suction flaskflask-increases increases rate of filtration. Suction funnel - allo�vs filtration under acuum Silica crucible - heating or burning solid substances Sintered Sinter ed glass crucible crucible - used for filtration, filtration, ding and weighing weighing of substances substa nces withouttransfer Oen/furnaces-used Oen/furnaces-u sed for ding substances to reproducible weight
2(b)(i)
Moles of siler chloride= chlo ride= (08402/1435) mol= 00059 00 059 mol
2(b)(ii)
Moles of KCI= 00059 mol
2(b)(iii)
Mass of KC KCII = (000 ( 00059 59 x 7 4.5 4.55) 5) g= g= 04398 g % KCI = (04398/0 (04398/0450) 450) x 100= 97 33 %
2(c
Determination Determi nation of the amount of phosphor phosphorous ous in fertilizer
2(d)
, and are the Mono Monochrom chromato ato beam splite spliterr and reference cell, respectiely
2(e)
Using A= Ec, c= (7/(840 /(8400 0 x 1)) mol dm·3= 833 x 10 10··5 mol dm·3.
CAPE Chemist Chemistry ry June 2018 U2 P2 Q3 - Ans Answer wer
3(a)(i)
I, II I, IV and V are Cl (g, H (g ,) titanium anode, steel/nickel cathode and NaOH/NaC respectively.
3(a)(ii)
At I: 2Cl·(aq- Cl g + 2e·. At IV: 2H 2H(aq) + 2e·- H g)
3(a)(iii)
Hydroen and chlorine would wou ld spontaneously inite init e H (g + Cl (g g- 2HCl 2HCl (g
3(b)
Bleachin aents herbicides an andd pesticides
3(c)
Risk of pollution fr from om asbestos NaOH, chlorine
2
2
2
2
2
2
CAPE Chemistry June 2018 U2 P2 Q4 - Answe Answerr 4(a)(i)
I
H3 c
H
but 1-ene
"c
H
,c� ,H
H
cis-2-butene
C
C
trans-2-butene
H I I I - I I I
4(a)(iii)
C� ,
CH3
H
4(a)(ii)
H
O
Optical isomerism becau because se butan-2-ol contains a chiral carbon. carbo n.
4(b) 0
0
-H20 HO C(CH4COH + NC)sNH2 . 0
0
NC(CH4CNH(CH2 NH n
Fomation of the amide bond between 1,6-diaminohane and hexane-16dioic acid results in the loss of a water molecule
CAPE Chemistry June 2018 U2 P2 QS - Answe Answerr 5(a)(i) 5 (a ) (i i )
The M and M+2 peaks suggest the presence of either chlorine or bromine. Since the peaks at 108 (M) and 110 (M+2) have almost the same intensity, this says sa ys that bro bromine mine is present
5(a)(iii)
The relative isotopic abundances of 79Br and 81Br are 50-50
5(b)(i)
The vapour pressure of a component of a mixure is equal to the vapour pressure of the pure component at that temperature multiplied by its mole fraction in the mixure.
5(b 5( b)(ii)
Positive deviation from Raoult's law occurs when the vapour pressure of a mixure is higher than expected for an ideal mixure This higher vapour pressure is as a result of there being weaker intermolecular forces between ethanol and cyclohexane �hen compared to the pure substances These weaker weak er intermolecular force forcess in the mix mixure ure are as a result of the diferences in polarity polar ity between ethanol ethano l and cyclohexane molecules
5(b)(ii) 81
Boiling temperature Vapour 78 °
Liquid
648 °
100% EtOH 0%C6H 12
0430 EtO EtOH H 0570 EtOH
100%C6H12 0% EtOH
CAPE Chemistry June 2018 U2 P2 Q6 - Answ Answer er 6(a)
Sucrose is nverted to glucos glucose e and fructose by the action of enzymes present in yeast ie. C 12H 22 01 1 + H20 - 2C6H1206 . The fructose and glucose sugars then react via the action of another enzyme in yeast to produce ethanol and carbon carbon dioxide ie i e C6H120 - 2C2H50H + 2C 2C0 02•
6( b)
Fractional distillation
6(c)
The ethanol present in wine ca can n be oxidi oxidized zed to etha ethanal nal and ethan ethanoic oic acid
6(d)) 6(d
Two advantages: Gla Glass ss can be re-used and rec recycl ycled ed which whi ch leads to a reduction in solid waste, and recycling glass means that some of the manufacturing costs co sts are reduced Two disadvantages: Glass manuacture is vey expensive and glass is non biodegradable
6(e)
Cirrhosis of the liliver ver and hea disease
