Question

We recently did a lab testing the reaction between KMnO₄, H₂C₂O₄ and H₂O. These were the reactions:

KMnO4 ~0.02M	H2C2O4 ~0.5M	H2O
Experiment 1	10.0mL	20.0mL	0.0mL
Experiment 2	5.00mL	20.0mL	5.0mL
Experiment 3	10.0mL	10.0mL	10.0mL

These were the times (in minutes) recorded idnetifying a color change:

Exp. 1: trial 1 3:15, trial 2 3:43

Exp. 2: trial 1 4:28, trial 2 4:43

Exp. 3: trial 1 6:30, trial 2 6:47

We are asked to determine:

1) The order of the reaction with respect to [KMnO₄].

2) The order of the reaction with respect to [H₂C2O₄].

3) The overall order of the reaction.

4) The rate constant.

5) The rate of the reaction if you were to mix

30mL of H₂C₂O₄

15mL of KMnO₄

5mL of H₂O

Answer 1

Rate of reaction

From the given data,

1) Experiment 1 and 2, [H2C2O4] is constant and KMnO4 is halved, no change in rate of reaction observed,

order with respect to KMnO4 = 0

2) Experiment 1 and 3, [KMnO4] is constant and H2C2O4 is halved, the rate of reaction is doubled,

order with respect to H2C2O4 = inverse relation

3) Overall rate law becomes,

rate = k/[H2C2O4]

4) rate constant k = 3.3 x 5 = 16.5 M^2/s

5) rate when,

[H2C2O4] = 30/50 = 0.6

rate = 3.3/0.6 = 5.5 M/s