CIE Nov 2017 v2 Paper 4 Q1

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Answer all the questions in the spaces provided. The compound chlorine dioxide, Cl O2, can be prepared by the reaction shown. PMT NaCl O2 + 1 2Cl 2 Cl O2 + NaCl (a) Using oxidation numbers, explain why this reaction is a redox reaction.[2] (b) The central atom in the molecule of Cl O2 is chlorine. Draw the dot-and-cross diagram for Cl O2. Show outer electrons only. [2] (c) The reaction between Cl O2 and F2 is shown. 2Cl O2 + F2 2Cl O2F The rate of the reaction was measured at various concentrations of the two reactants and the following results were obtained. experiment [Cl O2] / mol dm3 [F2] / mol dm3 1 2 3 0.010 0.025 to be calculated 0.060 0.060 0.040 initial rate / mol dm3 s1 2.20103 to be calculated 7.04103 The rate equation is rate = k [Cl O2][F2]. (i) What is meant by the term order of reaction with respect to a particular reagent?[1]UCLES 2017 9701/42/O/N/17<br /> PMT (ii) Use the results of experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. rate constant, k =units[2] (iii) Use the data in the table to calculate the initial rate in experiment 2, [Cl O2] in experiment 3. initial rate =mol dm3 s1 [Cl O2] =mol dm3 [2] (d) (i) What is meant by the term rate-determining step?[1] (ii) The equation for the reaction between Cl O2 and F2 is shown. 2Cl O2 + F2 2Cl O2F rate = k [Cl O2][F2] The mechanism for this reaction has two steps. Suggest equations for the two steps of this mechanism, stating which of the two steps is the rate-determining step. step 1step 2rate-determining step =[2] (e) By considering the rate equation, explain why the rate increases with increasing temperature.[1]UCLES 2017 9701/42/O/N/17 [Total: 13] [Turn over<br />

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