Chemical kinetics question???

Question

I need a little help with a kinetics question,

A complex ion, [Cr(NH3)5Cl]^2+ , reacts with OH^- ion in aqueous solution,

[Cr(NH3)5Cl]^2+ (aq)+OH^- (aq) ~~> [Cr(NH3)5(OH)]^2+ (aq)+ Cl^- (aq)

The following data were obtained for the reaction at 25C

time, min..........[Cr(NH3)5Cl]^2+ ,M

0......................1.00

6......................0.657

12....................0.432

18....................0.284

24....................0.186

30....................0.122

36....................0.0805

What is the order of the reaction with respect to the [Cr(NH3)5Cl]^2+ ion???

thanks for your help :)

Answer 1

Plotting the natural logarithm of the concentration vs time gives a near perfect straight line (99.99% correlation). This means the reaction is first order with respect to [Cr(NH3)5Cl]^2+. The kinetic constant (negative of the slope) is 0.07 /min, by the way.

Plotting either the concentration or the reciprocal of the concentration vs time gives curves, meaning the reaction can be neither zero nor 2nd order.