Question

If a reaction has the experimental rate expression rate = $K\left[A{]}^2\right[B]$, if the concentration of A is doubled and the concentration of B is halved, the what happens to the reaction rate:-

• A. Rate becomes double
• B. Rate becomes eight times
• C. Rate becomes tripled
• D. No change in rate

Answer 1

The correct option is A Rate becomes double

$r=K\left[A{]}^2\right[B]$
After new condition
$r^1=K\left[2A{]}^2\right[\frac{B}{2}]$
$=4\times \frac{1}{2}\frac{K\left[A{]}^2\right[B]}{R}$
$r_1=2r$
thus $r=2r$
rate doubles.