1. Unit 1 PPA 2 The effect of temperature on reaction rate

2. The effect of temperature on reaction rate. (Unit 1 PPA2) (1) What colour change is seen in this reaction?(1) Purple to colourless. (2) (a) The permanganate ion is purple. (b) The purple permanganate ion is replaced by the colourless manganese(II) ion. (3) The time taken for the purple colour to disappear is measured each time the experiment is carried out. (a) How is the time turned into a rate for the reaction? (b) What unit is used to measure the rate? (3) (a) Rate = 1 / time. (b) The unit of rate is s -1. The aim of this experiment is to find the effect of varying the temperature on the rate of reaction between oxalic acid and an acidified solution of potassium permanganate : 5(COOH) 2 (aq) + 6H + (aq) + 2MnO 4 - (aq) 2Mn 2+ (aq) + 10CO 2 (g) + 8H 2 O(l) (2) (a) Which reactant is purple in colour? (b) Why does the purple colour disappear?

3. 0 20 40 60 80 Temperature ( o C) 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 Rate (s -1 ) (4) The graph shows the a students results. Why was the reaction not carried out at room temperature (about 20 o C) ? (4) The reaction is very slow at room temperature and so it would take too long to time. (5) Use the information in the graph to give the time taken for the purple colour to disappear when the temperature was 50 o C. (5) The rate = 0.011 s-1 So the time = 1 / 0.011 = 90.9 seconds (6) Use the information in the graph to estimate the temperature rise needed to double the reaction rate. (6) A rise of about 10 o C is required to double the reaction rate.