Suppose you have measured the kinetics of the reaction, 2 A + B → C.

Question

You measure the change in the B-concentration with time and determine the rate law is zeroth order in A and second order in B and has a rate constant of k = 0.0188 M^-1 s^-1. 

 

If the A-concentration is 0.24 M and the B-concentration is 0.2 M, what is the rate (in M s^-1)?  



{Enter your value with two significant figures. You may want to use E-notation to enter your value.)

Answer 1

Knowing the order of the reaction allows us to write the rate equation. Thus, since it is zero order in A, the [A] will not appear in the rate equation as the rate is independent of A. Since it is 2nd order in B, the [B] will be squared in the rate equation.

Rate = k[B]²

Rate = 0.0188 M^-1s^-1[0.2 M]²

Rate = 0.000752 M/s = 7.5x10^-4 M/s (2 sig. figs. and E-notation)