Unit 1

PPA 2The effect of

temperature on reaction rate

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) + 2MnO4-(aq) 2Mn2+(aq) + 10CO2(g) +

8H2O(l)

(2) (a) Which reactant is purple in colour?

(b) Why does the purple colour disappear?

0 20 40 60 80

Temperature (oC)

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 20oC) ?

(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 50oC.

(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 10oC is required to

double the reaction rate.