AS CHEMISTRY Paper 2 Organic and Physical Chemistry

AS CHEMISTRY Paper 2 Organic and Physical Chemistry Time allowed: 1 hour 30 minutes Materials For this paper you must have: • the Periodic Table/Data Sheet, provided as an insert (enclosed) • a ruler with millimetre measurements • a scientific calculator, which you are expected to use where appropriate. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • All working must be shown. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 80. Advice You are advised to spend about 65 minutes on Section A and 25 minutes on Section B. Section A Answer all questions in this section. box This question is about rates of reaction. Potassium manganate(VII), KMnO4, reacts with sodium ethanedioate, Na2C2O4, in the presence of dilute sulfuric acid. 2 MnO –(aq) + 16 H+(aq) + 5 C O 2–(aq)  2 Mn2+(aq) + 8 H O(l) + 10 CO (g) The reaction mixture is purple at the start and goes colourless when all the MnO –(aq) ions have reacted. The rate of reaction can be measured as 1000 where t = the time taken for the mixture t to go colourless. A student investigated how long it takes for this reaction mixture to go colourless at different temperatures. The same concentrations and volumes of each reagent were used in an experiment at each temperature. Table 1 shows the results. Table 1 Temperature / C 32 38 44 54 67 Time t / s 155 85 50 22 9 1000 t 6.45 11.8 20.0 45.5 . Complete Table 1. [1 mark] . State the independent variable in this investigation. [1 mark] . The student noticed that the temperature of each reaction mixture decreased during each experiment. Suggest how the student calculated the temperature values in Table 1. [1 mark] . Use the data in Table 1 to plot a graph of 1000 against temperature. t [3 marks] box 0 1 . 5 Use your graph in Question 01.4 to find the time taken for the mixture to go colourless at 60 C Show your working. [1 mark] Time t s Turn over ► . The investigation shows that increasing the temperature causes the rate of reaction to increase. Explain why a small increase in temperature causes a large increase in the rate of reaction. box [2 marks]