In aqueous solution, chlorine dioxide, ClO2, reacts with hydroxide ions as shown. 2ClO2 + 2OH- → ClO3- + ClO2- + H2O A series of experiments is carried out using different concentrations of ClO2 and OH-. The table shows the results obtained. experiment [ClO2] /mol dm-3 [OH-] /mol dm-3 initial rate /mol dm-3 min-1 1 0.020 0.030 7.20 × 10-4 2 0.020 0.120 2.88 x 10-3 3 0.050 0.030 4.50 x 10-3 Explain the term order of reaction. .........................................................................................................................................................

1. (a)(i)In aqueous solution, chlorine dioxide, ClO2, reacts with hydroxide ions as shown. 2ClO2 + 2OH- → ClO3- + ClO2- + H2O A series of experiments is carried out using different concentrations of ClO2 and OH-. The table shows the results obtained. experiment [ClO2] /mol dm-3 [OH-] /mol dm-3 initial rate /mol dm-3 min-1 1 0.020 0.030 7.20 × 10-4 2 0.020 0.120 2.88 x 10-3 3 0.050 0.030 4.50 x 10-3 Explain the term order of reaction. .........................................................................................................................................................[1]
2. (a)(ii)Use the data in the table to determine the order of reaction with respect to each reactant, ClO2 and OH-. Explain your reasoning. ........................................................................................................................................................... ........................................................................................................................................................... ........................................................................................................................................................... ...........................................................................................................................................................[2]
3. (a)(iii)Use your answer to (a)(ii) to construct the rate equation for this reaction. rate = .................................................................................................................................................[1]
4. (a)(iv)Use your rate equation and the data from experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. k = .............................................................. units ...........................................[2]
5. (b)The decomposition of benzenediazonium ions, C6H5N2+, using a large excess of water, is a first-order reaction. The graph shows the results obtained. [Figure showing concentration-time graph for C6H5N2+]
6. (b)(i)Draw the structure of the organic product formed in this reaction.[1]
7. (b)(ii)Use the graph to determine the rate of reaction at 100 s. Show your working. rate = ............................................................. moldm-³s-1[1]
8. (c)Sketch a concentration-time graph for a zero-order reaction. Use your graph to suggest how successive half-lives for a zero-order reaction vary as the concentration of a reactant decreases. Indicate this by placing a tick (✔) in the appropriate box in the table. [Figure with axes for concentration vs time] successive half-lives decrease no change in successive half-lives successive half-lives increase[1]

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