Question

Four experiments were conducted to discover how the initial rate of consumption of BrO₃^- ions in the reaction BrO₃^-(aq) + 5Br^-(aq) + 6H⁺(aq) à 3Br₂(aq) + 3H₂O(l) varies as the concentration of the reactants are changed. Use the data given below to determine the average rate constant and write the rate law for this reaction.

Experiment	[BrO3-] (M)	[Br-] (M)	[H+] (M)	Initial rate (M/s)
1	0.10	0.10	0.10	0.0012
2	0.20	0.10	0.10	0.0024
3	0.10	0.30	0.10	0.0035
4	0.20	0.10	0.15	0.0054

Answer 1

in experiment 1 and 3 , the concentration of BrO3^-1 but the conentration of Br- is increased 3 times. rate is also increased three times. So the reaction is 1st order with respect to Br-.

In experiment 1 and 2 the concentration of BrO3^-1 is doubled and consequently the rate is also doubled. So, the reaction is ist order with respect to BrO3^-1.

rate = k [BrO3^-1][Br-]

This is the rate law

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to find out the averate rate constant consider experiment 1

rate = k [BrO3^-1][Br-]

k=rate/ [BrO3^-1][Br-]

   = 0.0012 M/s/[0.1][0.1]= 0.12 M-1s-1