Question

Which order reaction obeys the expression $t_{1/2}=\frac{1}{k.a}$in chemical kinetics?

($a$ = concentration of reactant, $k$ = rate constant, $t_{1/2}$ = half-life)

• A. $0$
• B. $1$
• C. $2$
• D. $1\frac{1}{2}$

Answer 1

Answer: (C)

$2$

For $n^{th}$ order reaction, the relationship between the half life period and the concentration is $t_{1/2}=\frac{1}{k.a^{n-1}}.$

But $t_{1/2}=\frac{1}{k.a}$

Hence, $n-1=1$ or $n=2$.

Hence, for a second order reaction, the half life period is inversely proportional to the concentration.

Therefore, the correct option is C.