Using the data in the table, determine the rate constant of the reaction and select the appropriate units.

Question

A+2B->C+D

Trial...[A](M)...[B](M)...Rate(M/s)

1...0.350...0.320...0.0102

2...0.350...0.640...0.0102

3...0.700...0.320...0.0408

k=

Answer 1

Since keeping the concentration of A constant and doubling B makes no change in the rate, the reaction rate is independent of the concentration of B or is zero order in B.

Doubling the concentration of A, keeping B constant, results in increasing the reaction rate by a factor of 4, and is second order in A.

This is consistent with the rate equation R = k [A]^2.

Solving for k = R / [A]^2. Putting in the given values gives k = 0.0102 / 0.350^2 = 0.0833 M^-1 s^-1

You should get the same result using 0.700 for the concentration and 0.408 for the rate.