The following data were obtained at 25° C for the reaction
C2H5Br + OH- ->C2H5OH + Br-
Determine the rate law for the reaction from these data.
[C2H5Br] [OH-] Rate
0.150 0.200 4.8 x 10-5
0.300 0.200 9.6 x 10-5
0.450 0.200 14.4 x 10-5
0.300 0.600 28.8 x 10-5
To determine the rate law for the reaction, we need to determine how the initial concentrations of the reactants ([C2H5Br] and [OH-]) affect the rate of the reaction.
To do this, we can compare the rates of the reaction when the concentrations of one reactant are kept constant and the concentration of the other reactant is varied.
Let's first consider the effect of [C2H5Br] on the rate of the reaction. We can compare the first three experiments where the [OH-] is constant at 0.200 M:
Experiment 1: [C2H5Br] = 0.150 M, Rate = 4.8 x 10^(-5) M/s
Experiment 2: [C2H5Br] = 0.300 M, Rate = 9.6 x 10^(-5) M/s
Experiment 3: [C2H5Br] = 0.450 M, Rate = 14.4 x 10^(-5) M/s
From these results, we can see that doubling [C2H5Br] (from 0.150 M to 0.300 M) doubles the rate of the reaction. Similarly, tripling [C2H5Br] (from 0.150 M to 0.450 M) triples the rate of the reaction. This indicates that the reaction rate is directly proportional to the concentration of C2H5Br.
Next, let's consider the effect of [OH-] on the rate of the reaction. We can compare experiments 2 and 4 where the [C2H5Br] is constant at 0.300 M:
Experiment 2: [C2H5Br] = 0.300 M, [OH-] = 0.200 M, Rate = 9.6 x 10^(-5) M/s
Experiment 4: [C2H5Br] = 0.300 M, [OH-] = 0.600 M, Rate = 28.8 x 10^(-5) M/s
From these results, we can see that tripling [OH-] (from 0.200 M to 0.600 M) triples the rate of the reaction. This indicates that the reaction rate is directly proportional to the concentration of OH-.
Based on these observations, we can conclude that the rate law for the reaction is:
Rate = k[C2H5Br]^1[OH-]^1
Therefore, the rate law can be written as Rate = k[C2H5Br][OH-]. Since the order of the reaction with respect to each reactant is 1, it is a first-order reaction.
This is a lot of typing for you just to check your work. If you have numbers give them to me and we can go from there. If you don't understand something go into that in detail and we can go from there.
The order is 1 with respect to both and order of 2 overall.