Question

The dimensions of rate constant of a second order reaction involves:

• A. neither time nor concentration
• B. only time
• C. time and concentration
• D. time square and concentration

Answer 1

Answer: (C)

time and concentration

For a second order reaction:

$2A\to product$
$Rate=K[A{]}^2$

$k=\frac{rate}{[A{]}^2}$

$=\frac{concentration}{time(concentration{)}^2}$

$=\frac{1}{time.concentration}$

So it involves both time & concentration. Except for first-order reactions, the unit of rate constant depends on the dimensions ($mo{l}^{1-n}.li{t}^{-1}.se{c}^{-1}$) concentration and time.

Where n= order of the reaction.