Edexcel A-Level Chemistry A2 B 2 2 Changing the Subject of an Equation Questions

Practise Edexcel IAL Chemistry changing the subject of an equation by rearranging rate expressions to calculate rate constants with matching units.

Exam points

Rearrange a rate equation to make k the subject, then calculate its value and units from experiment data.

[Maximum number: 2]

This question is about the reaction between nitrogen monoxide and oxygen.

\mathrm{NO}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{NO}_{2}(\mathrm{~g})

The results of a series of kinetics experiments are shown.

Table for Question Edexcel A-Level Chemistry A2 B 2 2 Changing the Subject of an Equation Questions question 1 — Edexcel A-Level Chemistry A2

The data for experiments 1-5 were plotted on a graph.

Figure for Question Edexcel A-Level Chemistry A2 B 2 2 Changing the Subject of an Equation Questions question 1 — Edexcel A-Level Chemistry A2

Calculate the rate constant for this reaction using the data from experiment 1 and your rate equation. Include units in your answer.

substitution or rearrangement

- answer and units

Example of a calculation:
$\begin{aligned} 0.040=\mathrm{k}(0.010)^{2}(0.05) \mathrm{k}=\frac{0.040}{(0.010)^{2}(0.05)} \end{aligned}$ $=8000 \mathrm{dm}^{6} \mathrm{~mol}^{-2} \mathrm{~s}^{-1}$
Allow units in any order
Allow $\mathrm{s}^{-}$
Allow $\mathrm{dm}^{6} / \mathrm{mol}^{2} \mathrm{~s}$ but not $\mathrm{dm}^{6} / \mathrm{mol}^{2} / \mathrm{s}$
Allow TE on a(iv) for both marks, units must match
order for M2
Correct answer with units scores 2, even if expression
in Q18(a)(iv) is incorrect

(2)

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Edexcel A-Level Chemistry A2 B 2 2 Changing the Subject of an Equation Questions question 1