Question

Which one of the following sets of units is appropriate for a second-order rate constant?

Answer 1

Answer:

C. L mol-1 s-1.

Explanation:

Hello,

In this case, a rate law has the following general form:

$r=kC^x_i$

Whereas r accounts for the rate measured in M/s units, k is the rate constant whose units depends on the order of the reaction, C the concentration of the species in M units, contributing to the rate and x the order of the reaction.

In such a way, since in this case x equals two (second-order rate), the units of k turns out:

$\frac{M}{s}=\frac{mol}{L*s}=k*(\frac{mol}{L}) ^2\\\frac{mol}{L*s}=k*\frac{mol^2}{L^2}\\\\k=\frac{L^2*mol}{mol^2*L*s} \\\\k=\frac{L}{mol*s}$

Which matches with C. L mol-1 s-1.

Best regards.