0620 s03 Qp 2 Model Answers Final

Centre Number

Candidate Number

Name

CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education

0620/02

CHEMISTRY Paper 2

May/June 2003 1 hour

Candidates answer on the Question Paper. No Additional Materials required

READ THESE INSTRUCTIONS FIRST Write your name, centre number and candidate number in the spaces provided at the top of this page. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 16.

FOR EXAMINER’S USE 1 2 If you have been given a label, look at the details. If any details are incorrect or missing, please fill in your correct details in the space given at the top of this page. Stick your personal label here, if provided.

3 4 5 6 TOTAL

This document consists of 16 printed pages. SP (SC) S33034/4 © CIE 2003

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2 1

For Examiner’s Use

The diagram shows part par t of the Periodic Table. Table. I

II

I II

Li Na K

IV C

Fe

Cu

Zn

V N

VI O S

VII

0

F Cl Br

He Ne Ar Kr

(a) Answer these questions using only the elements shown in the diagram. Write down the symbol for an element which

(i)

is a transition metal.

Fe

I

(ii)

forms an acidic oxide.

C

[I]

(iii)

has six electrons in its outer shell.

O

[I]

(iv)

has a giant covalent structure.

C

[I]

(v)

reacts rapidly with water.

Li

I

(vi)

has a higher proton (atomic) number than iron.

Cu

I

[6]









3


(b) Some uses of some non-metallic elements are show below. Draw lines between the boxes to link the elements to their correct uses. The first one has been done for you. element

use

oxygen

in light bulbs

argon

in oxygen tents in hospitals

chlorine

to kill bacteria in water purification

carbon (graphite)

in balloons

helium

as a lubricant [4]

(c) The structures of some halogen compounds are shown below.

Na+ Cl

I

Cl A (i)

Cl

Cl – Na+

Cl –

+

Cl –

Na

Na+

Cl – Na+ B

F F F

Br

F

F C

Describe the type of bonding in compound A.

covalent - NB 2 non-metals non- metals bonded bo nded to ether

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

[I]

(ii) State the simplest formula for compound C.

Br F or F Br

5 5 ................................................................................................................................... (iii)

Explain why compound B does not conduct electricity when solid but does conduct

I









4 2


A student investigates the reaction between zinc and hydrochloric acid. The hydrochloric acid is in excess. The student uses the apparatus shown in the diagram.

hydrogen gas

gas syringe

small test tube held by a piece of cotton

zinc power hydrochloric acid (a) What should the student do to start the reaction?

drop tube into acid or loosen cotton or allow zinc and acid to  mix, or let go of cotton

......................................................................................................................................[1] (b) The student reads the volume of gas in the syringe every minute. The results are shown in the table.

(i)

time in minutes

0

1

2

3

4

5

6

7

volume of gas in cm3

0

23

35

45

50

53

55

55

Plot the results on the grid on page 5.

[I]









5


60

50

40 3

m c / s a g f o e m u l o v

30

20

10

0

1

2

3

4

5

6

7

time/min (ii)

Draw the best curve through the points.

(iii)

Explain why the volume of gas stays the same after six minutes.

[I]

no more gas produced / reaction has stopped  all zinc used up ...............................................................................................................................[5]

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

(c) The student does the experiment again. The only difference is that the student uses warm, rather than cold, hydrochloric acid. On the grid, draw the shape of the graph you would expect for the experiment with the warm hydrochloric acid.

I I

I [2]

.

[I]









6


(d)) (i (d (i)) Balance the equation for the reaction between zinc and hydrochloric acid. Zn

+

2… HC

l

I x Zn + 2 x Cl + 2 x H atom →

ZnCl2

+

(ii) Name the compound which has the formula ZnCl2.

H2

zinc chloride

................................................................................................................................... (iii) Calculate the relative formula mass of ZnCl2.

Zn = 65 2 x Cl= 2x35.5 = 7I I36 [3] (e) Zinc is an element. State the meaning of the term element .

The best definition of an element is that all the atoms have  the same proton number ..................................................................................................................................[1]

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

[I]











7 3


The states of matter are solid, liquid and gas. The diagram below shows how the molecules are arranged in these three states. melting

A

B

C

SOLID

LIQUID

(a) State the name given to the change of state labelled (i) (ii) (iii)

GAS

evaporation or boiling or vaporisation (NB liquid -> gas) freezing or solidification (NB liquid to solid) B ............................................................................................................................... condens ing or condensati c ondensation on or liquefaction liqu efaction (NB gas to liquid) C condensing ................................................................................................................................

A ...............................................................................................................................

[3] (b) Which one of the following best describes the movement of molecules in the liquid state? Tick one box.

The molecules are not moving from place to place.

The molecules are sliding over each other.

The molecules are moving freely.









8


(d) Choose from the following list of substances to answer the questions below. bromine chlorine iron mercury sodium chloride sulphur Name a substance which is (i) (ii) (iii)

chlorine bromine a non-metallic liquid at room temperature. .................................. ............................................................... ............................. Sodium chloride ................. a compound which is a solid at room temperature. .................................. ...................................................

a gas at room temperature. .................................. ................................................................... .................................................... ...................

[3] (e) A student set up the apparatus shown in the diagram below. glass tube

X

cotton wool soaked in ammonia solution

rubber bung

cotton wool soaked in concentrated hydrochloric acid

The white solid is formed because the molecules of hydrogen chloride gas and ammonia gas move at random throughout the tube and eventually react with each other. (i)

State the name given to this random movement of molecules.

Diffusion

................................................................................................................................... (ii)

State the name of the white solid formed at X.

ammonium chloride

I









9

For Examiner’s

(g) The diagram below shows a simple apparatus that can be used for measuring the melting point of a solid. The liquid in the beaker is heated slowly and the temperature at which the solid B melts is recorded.

Use

A

small tube

stirrer

solid B

liquid

heat (i)

State the name of the piece of apparatus labelled A.

thermometer

................................................................................................................................... (ii)

Solid B melted at 155oC. Why would water not be a suitable liquid to put in the beaker when using this apparatus to find the melting point of solid B?

boiling point of water is too low to melt solid boiling point of water cannot get to I55 C ................................................................................................................................... ...................................................................................................................................

(iii)

I

Suggest why the liquid needs to be kept stirred.

I









10 4

For Examiner’s

Catalytic cracking is carried out by oil companies to produce high grade petrol. The process is carried out using an aluminium oxide catalyst. The reaction is a type of thermal decomposition.

Use

(a) Explain the meaning of (i)

thermal decomposition decomposition..

breaking down of a substance using heat

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

[I]

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

(ii)

catalyst.

substance which speeds up a reaction

................................................................................................................................... ..............................................................................................................................[2] (b) A typical ‘cracking’ reaction is C10H22

→

C8H18

+

C2H4

State the name of the unsaturated compound in this equation.

ethene

......................................................................................................................................[1] (c) The table shows some of the products obtained by cracking 100g of different ‘fractions’ under the same conditions.

products obtained / g per 100g of ‘fraction’ cracked ‘fraction’ cracked

hydrogen

methane

ethene

petrol

e th a n e

10

5

75

2

paraffin

1

15

30

23

0

6

20

17

di

l

I









11

For Examiner’s

(iii) Complete the equation for the cracking of ethane to produce hydrogen and ethene. C2H6

C H

2 4 ………………

→

+

H

2 ……………… [4]

Use

[2]

(d) Ethene can be polymerised to form poly(ethene). (i)

(ii)

Complete the equation below to show the structure of two units in the poly(ethene) molecule. H

H

C

C

H

H

+

H

H

C

C

H

H

→

H H H H C C C C H H H H or -CH 2 -CH 2 -CH -C H2 -CH 2

State the name given to this type of polymerisarion.

addition

...............................................................................................................................[2]

5

A precipitate may be formed when two aqueous solutions are mixed. The colour of these precipitates may be used to identify particular aqueous ions. (a) Complete the following table.

i o n un der t es t iron(II)

iodide

chloride

I

solution to be added to test for the ion

sodium hydroxide or  a ueou ueouss amm ammon onia ia silver nitrate or lead  nitrate silver nitrate

colour of precipitate

green or green-grey  precipitate ellow precipitate ellow precipitate white precipitate

I











12

For Examiner’s

(b) When a solution of iron(III) chloride is added to a solution of sodium hydroxide, a precipitate of iron(III) hydroxide is formed and sodium chloride remains in solution.

sodium chloride solution

iron(III) hydroxide

Explain how you would obtain a pure dry sample of sodium chloride from this mixture. You may use diagrams di agrams to help with your explanation.

I filtration

fil filter ter a er iron(iii) hydroxide [I]

sodium chloride solution 2 Evaporate water  from sodium 

[I]

water evaporating

Use









13 6


This question is about different metals. The list below shows part of the metal reactivity series . potassium magnesium aluminium zinc iron c op per

more reactive

less reactive

(a) From this list, choose a metal which is extracted using electrolysis.

Any one of the top three K, Mg or AL

......................................................................................................................................[1]

I

(b) Two thousand years ago, people were able to extract extract iron and copper from their ores. They were not able to extract aluminium. alumini um. Suggest why they were not able to extract aluminium from its ore.

they did not have electricity or they did not know about electrolysis .......................................................................................................................................... or......................................................................................................................................[1] they did not know the th e metal existed (c) Uranium is between magnesium and zinc in the reactivity series. Equal sized strips of magnesium, uranium and zinc were placed in hydrochloric acid. The hydrochloric acid was the same concentration. The results are shown in the table. (i)

Complete the result for uranium and hydrochloric acid.

I









14

For Examiner’s

(d) Metals high in the reactivity series react readily with oxygen. Name the compound formed when magnesium reacts with oxygen.

Use

Magnesium oxide

......................................................................................................................................[1] (e) Copper is alloyed with tin to make bronze. (i)

State what is meant by the term alloy .

Mixture of different metals

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

I

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

(ii)

Suggest why metals are often used in the form of alloys.

because harder or stronger or less malleable or tougher or more resistant to corrosion or heat or electrical resistance increased. ................................................................................................................................... ...................................................................................................................................

...............................................................................................................................[2] (f)

I

Zinc can be extracted by heating zinc oxide with carbon. ZnO

+

C

→

Zn

+

CO

Explain why carbon is a reducing agent (reductant) in this reaction.

removes ox gen from zinc zinc oxide, it is reduced reduced to zinc.

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

I









15


(h) Magnesium is in group II of the Periodic Table. (i)

Draw a diagram to show the electronic structure of magnesium.

Mg 2+8+2 (ii)

[I]

Explain what happens to the magnesium atom when it reacts and forms a magnesium ion.

loses two electrons oror loses its valenc electrons or forms Mg 2+ by losing electrons

...............................................................................................................................[3]

[2] I

+ I









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Summary of Examiner’s Examiner ’s Notes in IGCSE Chemistry Paper 2 June 2003 Page: 2 Q1 (a) i

Any one from Fe, Cu and Zn

Q1 (a) ii

Most non-metals except hydrogen and noble gases

Q1 (a) iii an element in Group VI, O, S Q1 (a) iv Only carbon in table above Q1 (a) v

Metals in Group I Li, Na and K









Page: 5 Q2 (b) i

NB every square = 1 cm³

Q2 (b) ii

Smooth curve and through origin (0, 0)

Q2 (c)

The reaction will go faster but because the amounts of chemicals are the same it will produce the same final volume of gas. Faster initial rate (steeper slope initially) through (0, 0) ends up at 55cm³

Page: 6 Q2 (d)

I x Zn + 2 x Cl + 2 x H atom









Q3 (b)

They are close together but can move past each other - so sliding over each other is a good description.

Q3 (b)

This relates to gases where the molecules are far apart and the intermolecular forces are very weak

Page: 8 Q3 (d) ii

bromine and mercury are both liquids at room temperature but mercury is a metal

Q3 (d) iii

in fact it is the only compound; all the others are elements

Q3 (e)

ammonia molecules have moved further in the same time









Page: 10 Q4 (a) ii Idea of increasing rate is essential. NOT alters or changes rate. Q4 (b)

Cn H2n + 2 alkane

Q4 (b)

CnH2n alkene

Q4 (c)

greatest amount of petrol per 100g

Q4 (c) ii Must have units









Page: 13 Q6 (a)

K is potassium

Q6 (b)

A specific comment is needed, NOT a general comment - 'they did not have the right technology'

Q6 (c) i

any statement that indicates that the reactivity is between magnesium and aluminium

Q6 (c) ii

'Atoms' is essential; not molecules or compounds

Q6 (c) ii

The best answer is; isotopes are atoms of the same element which have the same proton number but different nucleon numbers

0620 s03 Qp 2 Model Answers Final

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