Paper 2 June 2000

Answer guide for O Level Chemistry (5070/2) – Paper 2 Theory June 2000

A1(a)

Sulphur dioxide

1

(b)

Magnesium oxide

1

(c )

iron

1

(d)

potassium hydroxide (A ( Allow magnesium oxide and lithium)

1

(e )

lithium

1

A2(a A2(a))

Same Same proto roton n or or ato atom mic numb umber / varie riety of sam samee ele eleme men nt an and diff differ eren entt mas masss num numbe berr / dif diffe fere rent nt numb number er of neut neutro rons ns (per (per atom atom))

1

6 protons, 6 electrons and 7 neutrons

1

Carbon dioxide + water —> —> glucose + oxygen

1

Any two from: Needs sunlight Needs chlorophyll Catalysed by enzymes

2

Any three from: Long chain hydrocarbons are broken down, in a reaction called cracking, at high temperature, in the presence of a catalyst

3

(b)

butene

1

(c )

C3H6

1

(d)

pentene / hexene

1

(e )

double bond shown as two pairs between carbon atoms

1

all of the other electron structure correct

1

(f)(i)

C2H4 + H2O —> C2H5OH

1

(ii)

addition / hydration

1

A4(a)

CaCl2

1

MgCl2

1

mole HCl = mol NaHCO3 = 3.00 x 0.100 = 0.300

1

volume = 0.300 dm 3 / 300 cm 3

1

(c )

Any acid

1

(d)

calcium hydroxide / calcium oxide

1

(c )

A3(a)

(b)

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© UCLES 2002  

Answer guide for O Level Chemistry (5070/2) – Paper 2 Theory June 2000

A5(a)

Fe2+

1

oxidation number of Fe has increased / Fe 2+ has lost electrons

1

(b)

changes colour from colourless to yellow / orange / brown

1

A6(a)

2NaN3(s) —> 2Na(s) + 3N 2(g) balanced equation

1

correct state symbols

1

2 mole NaN3 gives 3 mole N 2

1

65 x 2 g of NaN3

1

gives 3 x 24 dm 3 N2 = 72 dm3

1

mole ratio H : N = 2.33 : 6.98

1

empirical formula is HN3

1

(ii)

NaN3 + HCl   —> HN3 + NaCl

1

A7(a)

calcium nitrate and water

1

(b)

No since the mass is still decreasing

1

(c )

The line must always be beneath and the same shape as the original 1

(d)

The reaction is too fast

1

(e )

gas syrin ringe or in inverted ted measuring cylin linder fu full of of wa water to to collec lect gas

1

suitable container for acid and calcium carbonate

1

method works i.e. no leaks anywhere

1

(b)

(c)(i)

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© UCLES 2002  

Answer guide for O Level Chemistry (5070/2) – Paper 2 Theory June 2000

B8(a) (b)

(c )

1 mole gives 890 kJ, so 16 g gives 890 kJ

1

0.32 g gives 17.8 kJ

1

bond breaking is endothermic

1

bond making is exothermic

1

more energy released than absorbed

1

carbon monoxide and water

1

(d) H

H

C

H

H

(e )

four shared pairs with hydrogen atoms

1

complete structure correct

1

Any two from: Hydrogen chloride Chloromethane Dichloromethane Trichloromethane Tetrachloromethane

2

B9(a)

2Y + H2SO4  —>

(b)

X

(c)(i)

(d)

Page 3 of 4

Y2SO4

+ H2

forms a coloured compound

1 1

Any two from: Forms two different ions Forms two chlorides Has a high density

2

positive ions

1

in a sea of electrons

1

electrical conductivity – electrons free to move / electrons are delocalised

1

malle malleab abil ility ity – ato atoms ms or ions ions can can sli slide de past past each each othe otherr ver very y eas easily ily

1

copper does not react with steam iron reacts reversibly to form hydrogen

1

© UCLES 2002  

Answer guide for O Level Chemistry (5070/2) – Paper 2 Theory June 2000

B10(a)

ester

1

(b)(i)

contains a carbon-carbon double bond

1

(ii)

bromine

1

with saturated fat stays orange

1

with unsaturated fat changes from orange to colourless

1

oleic acid because it is unsaturated

1

stearic acid is saturated

1

boil / heat

1

with aqueous sodium hydroxide

1

(d)

polyester / terylene t erylene

1

B11(a) B11(a)(i) (i)

SiC has silico silicon n and and carbo carbon n combi combined ned,, diamo diamond nd only only has has carbo carbon n /  SiC is a compound and diamond is an element / have different bond lengths 1

(iii) (c )

both have a tetrahedral carbon atom / coordination number of carbon is 4 / have the same bond angles / both are macromolecules 1 Any two from: High melting point Hard Non-conductor of electricity Insoluble in water

2

(c)(i)

quartz / sand

1

(ii)

3 moles of carbon makes 1 mole of SiC

1

36 g of carbon makes 40 g of SiC

1

So 18 tonnes of carbon makes 20 tonnes of SiC

1

(b)

(d)

Page 4 of 4

Two

from these: Water, carbon monoxide, carbon dioxide, silicon dioxide

© UCLES 2002  

2