Question

A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reaction is

Doubled

Reduced to half?

Answer 1

For a reaction, $A\to Products$
Rate $=k[A{]}^2=k{a}^2$
(i) When concentration of A is doubled
i.e., [A] = 2a
Rate $=k(2a{)}^2=4k{a}^2$
Rate of reaction becomes 4 times

When concentration of A is reduced to $\frac{1}{2}$
i.e. $\left[A\right]=\frac{1}{2}a$
Rate $=k{\left(\frac{a}{2}\right)}^2=\frac{1}{4}k{a}^2$
Rate of reaction becomes $\frac{1}{4}$ times i.e. reduced to one fourth.