AUTOCATALYTIC REACTION BETWEEN PERMANGANATE AND OXALIC


AUTOCATALYTIC REACTION BETWEEN POTASSIUM PERMANGANATE AND OXALIC ACID


THEORY:

An autocatalytic reaction, where one of the reaction products catalyzes the reaction itself, the rate of reaction is low initially until sufficient products have formed to catalyze the reaction.

 The reaction between potassium permanganate and oxalic acid is catalyzed by manganese ion formed.

2KMnO4 + 5H2C2O4 + 3H2SO4 = K2SO4 + 2MnSO4 + 10CO2 + 8H2O


PROCEDUR:

1-   Prepare and thermostat the following mixtures at 25 °C.












0.1 M Oxalic acid
100
100
100
100
0.2 M MnSO4
0
0
25
25
1.0 M H2SO4
10
10
10
10
Distilled water
40
65
15
40
0.02 M KMnO4
50
25
50
25
Total volume
200
200
200
200


2-  Withdraw 10 ml of mixture and excess of KI, 10%, into conical flask.
3- Titrate the liberated iodine with standard sodium thiosulphate solution, 0.01 M, using starch as indicator.
4- Repeat steps (2), (3) at variant periods for each mixture. 

CALCULATIONS:

1-   Plot a graph of time against the titre of sodium thiosulphate (equivalent to permanganate in mixture) for each mixture.
2- Comment on the results from the graph.