Chemistry 9701/42 — October/November 2018

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

questions

100

marks

120

minutes

Topics Nitrogen Compounds · Introduction to A Level Organic Chemistry · Analytical Techniques · Transition Elements · Group 2 · Chemical Energetics · +7 more

Q1Analytical TechniquesIntroduction to A Level Organic ChemistryHydrocarbonsReaction KineticsFree sample

(a)

An alkene, a carboxylic acid and a ketone, all of similar volatility, are mixed together. The mixture is then analysed by gas chromatography.

The gas chromatogram produced is shown.

Fig. 1.1

The separation of the three compounds depends on their relative solubilities in the liquid stationary phase. The liquid stationary phase is an alkane.

(i)

Complete the table to suggest which compound in the mixture is responsible for each peak J, K and L. Explain your answer by reference to the intermolecular forces of each compound.

peak	organic compound	explanation
J
K
L

(ii)

A student calculates the areas underneath the three peaks in the chromatogram.

peak	J	K	L
area / $\text{mm}^2$	46	18	28

The area underneath each peak is proportional to the mass of the respective compound.

Calculate the percentage by mass in the original mixture of the compound responsible for peak K.

(b)

Chlorobenzene can be prepared from benzene as shown.

Fig. 1.2

Aluminium chloride, $\text{AlCl}_3$ , catalyses this reaction.

(i)

Write an equation to show how $\text{AlCl}_3$ generates the electrophile needed in this reaction.

(ii)

Draw the mechanism of the reaction between this electrophile and benzene to form chlorobenzene. Include all relevant curly arrows and charges.

(iii)

Write an equation to show how the catalyst is regenerated.

(c)

(i)

Catalysts can be heterogeneous or homogeneous.

Explain what is meant by a homogeneous catalyst.

(ii)

Complete the table by placing one tick ( $\checkmark$ ) in each row to indicate the mode of action of the catalyst in each reaction.

	heterogeneous	homogeneous
Rh in the removal of $\text{NO}_2$ from exhaust gases of cars
$\text{Fe}^{3+}$ in the $\text{I}^- / \text{S}_2\text{O}_8^{2-}$ reaction

The rest of this paper

8 more questions

Q2Transition Elements7M
Q3Transition Elements13M
Q4Nitrogen Compounds · Group 2 · Chemical Energetics · Equilibria11M
Q5Group 2 · Electrochemistry · Equilibria · Organic Synthesis · Analytical Techniques22M
Q6Carboxylic Acids and Derivatives · Organic Synthesis · Nitrogen Compounds · Polymerisation9M
Q7Introduction to A Level Organic Chemistry · Polymerisation8M
Q8Introduction to A Level Organic Chemistry · Chemical Energetics · Nitrogen Compounds14M
Q9Nitrogen Compounds5M

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