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9701/42

Chemistry 9701/42 — October/November 2011

Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme

8
questions
100
marks
120
minutes

Topics Introduction to A Level Organic Chemistry · Nitrogen Compounds · Polymerisation · Hydrocarbons · Halogen Compounds · Chemical Energetics · +7 more

Q1HydrocarbonsHalogen CompoundsChemical EnergeticsIntroduction to A Level Organic ChemistryFree sample
(a)

The halogens chlorine and bromine react readily with hydrogen.

X2(g)+H2(g)→2HX(g)[X=Cl or Br]\text{X}_2(\text{g}) + \text{H}_2(\text{g}) \rightarrow 2\text{HX}(\text{g}) \quad [\text{X} = \text{Cl or Br}]
8M
(i)

Describe how you could carry out this reaction using chlorine.

(ii)

Describe two observations you would make if this reaction was carried out with bromine.

(iii)

Use bond energy data from the Data Booklet to calculate the ΔH⊖\Delta H^\ominus for this reaction when

X=Cl\text{X} = \text{Cl},

ΔH⊖=........................................ kJ mol−1\Delta H^\ominus = \text{........................................ kJ mol}^{-1}

X=Br\text{X} = \text{Br}.

ΔH⊖=........................................ kJ mol−1\Delta H^\ominus = \text{........................................ kJ mol}^{-1}
(iv)

What is the major reason for the difference in these two ΔH⊖\Delta H^\ominus values?

(b)

Some halogens also react readily with methane.

CH4(g)+X2(g)→CH3X(g)+HX(g)\text{CH}_4(\text{g}) + \text{X}_2(\text{g}) \rightarrow \text{CH}_3\text{X}(\text{g}) + \text{HX}(\text{g})
4M
(i)

What conditions are needed to carry out this reaction when X is bromine, Br?

(ii)

Use bond energy data from the Data Booklet to calculate the ΔH⊖\Delta H^\ominus of this reaction for the situation where X is iodine, I.

ΔH⊖=........................................ kJ mol−1\Delta H^\ominus = \text{........................................ kJ mol}^{-1}
(iii)

Hence suggest why it is not possible to make iodomethane, CH3I\text{CH}_3\text{I}, by this reaction.

(c)

Halogenoalkanes can undergo homolytic fission in the upper atmosphere.

3M
(i)

Explain the term homolytic fission.

(ii)

Suggest the most likely organic radical that would be formed by the homolytic fission of bromochloromethane, CH2BrCl\text{CH}_2\text{BrCl}. Explain your answer.

(d)

The reaction between propane and chlorine produces a mixture of many compounds, four of which are structural isomers with the molecular formula C3H6Cl2\text{C}_3\text{H}_6\text{Cl}_2.

Draw the structural or skeletal formulae of these isomers, and indicate any chiral atoms with an asterisk (*).

3M

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  • Q7Nitrogen Compounds · Analytical Techniques10M
  • Q8Polymerisation10M
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