Question

# Consider the reaction and the initial concentration and initial rate data below. BrO3-(aq) + 5 Br-...

Consider the reaction and the initial concentration and initial rate data below.

BrO3-(aq) + 5 Br- (aq) + 6 H+(aq) ® 3 Br2 (aq) + 3 H2O (l)

 Experiment [BrO3-], (M) [Br-],(M) [H+],(M) Initial Rate (M/sec) 1 0.10 0.10 0.10 1.2 x 10-3 2 0.20 0.10 0.10 2.4 x 10-3 3 0.10 0.30 0.10 3.5 x 10-3 4 0.20 0.10 0.15 5.4 x 10-3

Determine the rate law for this reaction

What is the overall order of the rate law?

Calculate the rate constant

Let Rate = k [ BrO3-]^a [Br-]^b [H+]^c   where a, b , c are respective orders

exp2 / exp1 = ( 2.4x10^-3) / ( 1.2x10^-3) = ( 0.2/0.1)^a

2 = 2^a , a= 1

exp 3/ exp 1 = ( 3.5x10^-3) / ( 1.2x10^-3)   = ( 0.3/0.1)^b

3 = 3^b , b = 1

exp 4/exp1 = ( 5.4x10^-3) / ( 1.2x10^-3) = ( 0.2/0.1)^1 ( 0.15/0.1)^c

2.25 = 1.5^c    , c = 2

Rate law is   Rate = k [BrO3-] [Br-] [H+]^2

overall order is 1+1+2 = 4

from exp1     1.2x10^-3 = k ( 0.1) ( 0.1) ( 0.1)^2

k = 12 L^3 / ( mol^3 s)

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