Chemistry 9701/42 — October/November 2014

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

questions

100

marks

120

minutes

Topics Analytical Techniques · Carboxylic Acids and Derivatives · Introduction to A Level Organic Chemistry · Nitrogen Compounds · Reaction Kinetics · Transition Elements · +6 more

Q1Reaction KineticsFree sample

(a)

The oxidation of nitrogen(II) oxide is shown in the equation.

2\text{NO(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{NO}_2\text{(g)}

The initial rate of this reaction was measured, starting with different concentrations of the two reactants. The following results were obtained.

experiment number	[NO] / $\text{mol dm}^{-3}$	[ $\text{O}_2$ ] / $\text{mol dm}^{-3}$	initial rate / $\text{mol dm}^{-3}\text{ s}^{-1}$
1	0.032	0.012	$4.08 \times 10^{-3}$
2	0.032	0.024	$8.15 \times 10^{-3}$
3	0.064	0.024	$3.28 \times 10^{-2}$
4	0.096	0.036

(i)

Use the data in the table to determine the order with respect to each reactant. Show your reasoning.

(ii)

Calculate the initial rate in experiment 4. Give your answer to two significant figures.

(iii)

Write the rate equation for this reaction.

(iv)

Use the results of experiment 1 to calculate the rate constant, $k$ , for this reaction. Include the units of $k$ .

(b)

(i)

On the following axes

draw two Boltzmann distribution curves, at two different temperatures, $T_1$ and $T_2$ ( $T_2 > T_1$ ),
label the curves and the axes.

Fig. 1.1

(ii)

State and explain, using your diagram, the effect of increasing temperature on the rate of reaction.

(c)

The compound nitrosyl fluoride, NOF, can be formed by the following reaction.

2\text{NO(g)} + \text{F}_2\text{(g)} \rightleftharpoons 2\text{NOF(g)}

The rate is first order with respect to NO and $\text{F}_2$ .
The reaction mechanism has two steps.

Suggest equations for the two steps of this mechanism, stating which is the rate determining slower step.

The rest of this paper

7 more questions

Q2Transition Elements13M
Q3Analytical Techniques · Chemical Energetics · Transition Elements · Equilibria16M
Q4Hydrocarbons · Carboxylic Acids and Derivatives · Hydroxy Compounds13M
Q5Halogen Compounds · Carboxylic Acids and Derivatives · Introduction to A Level Organic Chemistry · Nitrogen Compounds · Polymerisation15M
Q6Nitrogen Compounds · Analytical Techniques11M
Q7Carboxylic Acids and Derivatives · Nitrogen Compounds · Introduction to A Level Organic Chemistry · Reaction Kinetics · Chemical Energetics7M
Q8Analytical Techniques · Introduction to A Level Organic Chemistry12M

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