ZIMSEC A Level Chemistry Paper 2 November 2003

Question 101

[1 marks]mass spectrometry and bonding

2.000 g of lead was converted completely into lead(II) chloride, giving 2.682 g of the chloride. Taking

A_r(Cl) = 35.45

, the relative atomic mass of the lead is

A103.9
B207.9
C311.8
D415.8

Question 102

[1 marks]mass spectrometry and bonding

Lead melts at 327 °C but lead(IV) chloride melts at

-15

°C. This is because lead has

Aa giant ionic lattice while $PbCl_4$ is a giant covalent solid
Bstronger van der Waals forces than $PbCl_4$
Ca higher relative atomic mass than chlorine
Da giant metallic lattice while $PbCl_4$ is a simple covalent molecule

Question 103

[1 marks]mass spectrometry and bonding

In the mass spectrum of lead shown, the peaks at

m/e

= 204, 206, 207 and 208 are due to

Afragments of the lead atom
Bdoubly charged lead ions
Cisotopes of lead
Dimpurities in the sample

Question 104

[2 marks]mass spectrometry and bonding

Write the formulae (mass number nuclide notation) of the four lead nuclides present in this sample, whose peaks appear at m/e = 204, 206, 207 and 208.

Answer this when you sit the paper.

Question 105

[2 marks]mass spectrometry and bonding

The mass spectrum of this lead sample shows relative abundances of about 2% at m/e 204, 25% at m/e 206, 22% at m/e 207 and 51% at m/e 208. The average relative atomic mass of this sample is

Answer this when you sit the paper.

Question 106

[2 marks]mass spectrometry and bonding

The first lead sample (from the mass spectrum) has an average Ar of 207.2, while a second lead sample (from a lead(II) chloride experiment) has an Ar of 207.9. The most reasonable conclusion is that the two samples

Amay have slightly different isotopic compositions, though the difference is small and could partly reflect experimental error
Bmust be different elements entirely, since their Ar values are not identical
Ccannot both be lead, since Ar should always be a whole number
Dhave exactly identical isotopic compositions, and the small difference is impossible

Question 107

[1 marks]mass spectrometry and bonding

Suggest one way in which lead is released into the environment.

Answer this when you sit the paper.

Question 108

[2 marks]mass spectrometry and bonding

The average relative atomic mass of lead, 207.2, is calculated as a weighted mean of the isotope mass numbers (weighted by relative abundance) rather than a simple average of 204, 206, 207 and 208 because

Athe least abundant isotope should be given the greatest weight in the calculation
Ba simple average is mathematically impossible to calculate for more than two numbers
Cthe isotopes are not present in the sample in equal proportions, so each mass number must count according to how abundant it actually is
Dmass numbers must always be rounded to the nearest whole number before averaging

Question 201

[1 marks]energetics / Hess's law

The standard enthalpy changes of combustion of ethanol and ethanal are

-1370.7

and

-1167.3\ kJ\,mol^{-1}

respectively. The enthalpy change for

C_2H_5OH(l) + \frac{1}{2}O_2(g) \rightarrow CH_3CHO(l) + H_2O(l)

, in

kJ\,mol^{-1}

, is

A $-2538.0$
B $-203.4$
C $+203.4$
D $+2538.0$

Question 202

[1 marks]energetics / Hess's law

Ethanol is oxidised to ethanoic acid according to

C_2H_5OH + O_2 \rightarrow CH_3COOH + H_2O

. The mass of ethanol needed to give 5.0 g of ethanoic acid is

A5.00 g
B6.52 g
C7.67 g
D3.83 g

Question 203

[1 marks]energetics / Hess's law

The relative molecular mass of ethanoic acid measured in benzene is 120. This is because in benzene ethanoic acid

Areacts with the solvent
Bloses a molecule of water
Cforms hydrogen bonded dimers
Dionises completely

Question 204

[2 marks]energetics / Hess's law

Which statement below correctly gives Hess's Law?

Aa system at equilibrium always shifts to oppose any change imposed on it
Bthe enthalpy change of a reaction is always negative if the reaction releases a gas
Cenergy can be neither created nor destroyed, only converted from one form into another
Dthe total enthalpy change of a reaction is independent of the route taken, provided the initial and final conditions are the same

Question 205

[2 marks]energetics / Hess's law

Adding equations I and II together gives the overall equation for the bacterial oxidation of ethanol all the way to ethanoic acid. Write this overall equation.

Answer this when you sit the paper.

Question 206

[1 marks]energetics / Hess's law

The intermolecular force responsible for ethanoic acid molecules pairing up into dimers in benzene solution is

Answer this when you sit the paper.

Question 301

[1 marks]chemical equilibrium

4.0 mol of

NO_2

were placed in a

1\ dm^3

container and heated. At equilibrium,

2NO_2(g) \rightleftharpoons 2NO(g) + O_2(g)

, the mixture contained 0.8 mol of oxygen.

K_c

, in

mol\,dm^{-3}

, is

A0.09
B0.36
C0.85
D1.07

Question 302

[1 marks]chemical equilibrium

An equilibrium mixture of colourless

N_2O_4

and brown

NO_2

is immersed in ice-cold water. The mixture becomes

Adarker brown, as the pressure falls
Bpaler, as more $N_2O_4$ is formed
Ccolourless, as the reaction stops
Ddarker brown, as more $NO_2$ is formed

Question 303

[1 marks]chemical equilibrium

The dimerisation

2NO_2(g) \rightarrow N_2O_4(g)

is exothermic because

A $NO_2$ is a brown gas
B $N_2O_4$ has a lower relative molecular mass
Ca new $N-N$ bond is formed
Dthe number of gaseous molecules decreases

Question 304

[2 marks]chemical equilibrium

When the pressure on the equilibrium mixture of

N_2O_4

and

NO_2

is increased, the mixture becomes

Apaler, as the equilibrium shifts toward $N_2O_4$ , the side with fewer gas molecules
Bdarker brown, as the equilibrium shifts toward $NO_2$
Ccolourless, as the equilibrium mixture liquefies under pressure
Dunchanged in colour, since pressure does not affect a gas-phase equilibrium

Question 305

[2 marks]chemical equilibrium

The gas-phase structure of

N_2O_4

O_2N-NO_2

, a single N-N bond joining two planar

NO_2

units. The O-N-O bond angle within each

NO_2

unit is closest to

A90 degrees, since each nitrogen is octahedral
B120 degrees, since each nitrogen is trigonal planar with no lone pair
C109 degrees, since each nitrogen is tetrahedral
D180 degrees, since each nitrogen is linear

Question 306

[2 marks]chemical equilibrium

For the equilibrium

2NO_2(g) \rightleftharpoons 2NO(g) + O_2(g)

, the correct expression for

K_c

A $K_c = \dfrac{[NO]^2[O_2]}{[NO_2]^2}$
B $K_c = \dfrac{[NO][O_2]}{[NO_2]}$
C $K_c = [NO]^2[O_2][NO_2]^2$
D $K_c = \dfrac{[NO_2]^2}{[NO]^2[O_2]}$

Question 401

[1 marks]organic chemistry / polymers

A compound X of empirical formula

CH_3O

was vapourised at 400 K; 0.20 g of X occupied

107.2\ cm^3

at 100 kPa. The molecular formula of X is

A $C_2H_6O_2$
B $C_3H_9O_3$
C $C_4H_{12}O_4$
D $CH_3O$

Question 402

[1 marks]organic chemistry / polymers

Compound X,

C_2H_6O_2

, is oxidised mildly to a dicarboxylic acid. The structure of X is

A $CH_3CH_2OOH$
B $CH_3CH(OH)_2$
C $CH_3OCH_2OH$
D $HOCH_2CH_2OH$

Question 403

[1 marks]organic chemistry / polymers

Ethane-1,2-diol reacts with benzene-1,4-dicarboxylic acid to form a fibre used in clothing. The fibre is

Aa polyalkene
Ba polyamide
Ca polypeptide
Da polyester

Question 404

[2 marks]organic chemistry / polymers

Write a balanced equation for the reaction of X (ethane-1,2-diol,

HOCH_2CH_2OH

) with excess sodium.

Answer this when you sit the paper.

Question 405

[1 marks]organic chemistry / polymers

When compound X (ethane-1,2-diol) reacts with excess sodium, the gas evolved is

Ahydrogen
Bchlorine
Coxygen
Dcarbon dioxide

Question 501

[1 marks]organic chemistry / functional group tests

An orange precipitate is formed when 2,4-dinitrophenylhydrazine is added to

A $C_6H_5CONH_2$
B $C_6H_5CH_2CHO$
C $C_6H_5CH(OH)CH_3$
D $C_6H_5CH_2CO_2H$

Question 502

[1 marks]organic chemistry / functional group tests

A pale yellow precipitate of triiodomethane is obtained on warming alkaline

I_2

with

A $C_6H_5CONH_2$
B $C_6H_5CH_2CHO$
C $C_6H_5CH(OH)CH_3$
D $C_6H_5CH_2CO_2H$

Question 503

[1 marks]organic chemistry / functional group tests

Ammonia, which turns damp red litmus paper blue, is evolved when aqueous sodium hydroxide is heated with

A $C_6H_5CH_2CO_2H$
B $C_6H_5CONH_2$
C $C_6H_5CH_2CHO$
D $C_6H_5CH(OH)CH_3$

Question 504

[2 marks]organic chemistry / functional group tests

Warming with ethanol (in the presence of a little acid catalyst) gives a sweet-smelling ester with

A $C_6H_5CH_2CHO$
B $C_6H_5CH_2CO_2H$
C $C_6H_5CH(OH)CH_3$
D $C_6H_5CONH_2$

Question 505

[2 marks]organic chemistry / functional group tests

The ester formed when compound B,

C_6H_5CH_2CO_2H

, is warmed with ethanol is

Answer this when you sit the paper.

Question 506

[1 marks]organic chemistry / functional group tests

Heating compound C,

C_6H_5CONH_2

, with aqueous NaOH gives ammonia gas and the sodium salt of benzoic acid, named

Answer this when you sit the paper.

Question 507

[1 marks]organic chemistry / functional group tests

The type of organic product formed when 2,4-dinitrophenylhydrazine reacts with the carbonyl group of compound D is a

Answer this when you sit the paper.

Chemistry Paper 2 November 2003

Sit this paper online

The questions

Question 101

Question 102

Question 103

Question 104

Question 105

Question 106

Question 107

Question 108

Question 201

Question 202

Question 203

Question 204

Question 205

Question 206

Question 301

Question 302

Question 303

Question 304

Question 305

Question 306

Question 401

Question 402

Question 403

Question 404

Question 405

Question 501

Question 502

Question 503

Question 504

Question 505

Question 506

Question 507

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