Question

1) In a study of pyridine (C5H5N) with methyl iodide (CH3I) in a benzene solution, the following sets of initial rates were measured at 298 K for different initial concentrations of two reactants.

[C5H5N] [CH3I] rate

1 X 10-4 1 X 10-4 7.5 X 10-7

2 X 10-4 2 X 10-4 3.0 X 10-6

2 X 10-4 4 X 10-4 6.0 X 10-6

a) Write the rate law for the reaction

b) Calculate the rate constant k for the reaction

c) Predict the initial rate for a solution in which [C5H5N] = 5.0 X 10-5 M and [CH3I] = 2.0 X 10-5 M.

d) What is the rate for the reaction if the [py] is 0.05 M and the [CH3I] is 0.03

Answer 1

For (a), you have to let the orders of reaction with respect to pyridine and methyl iodide be arbitrary numbers a and b first. Then substitute the relevant values to find a and b.

For (b), use your answer in (a) and a set of values given by the question to determine the rate constant.

For (c) and (d), combine your answers for (a) and (b), and plug in the relevant values for the concentrations to find the rate.