Question

The half-life of a reaction is 50 minutes at a certain initial concentration. When the concentration is reduced to one-half, the half-life is found to be 25 minutes. The order of the reaction is:

• A. Zero
• B. One
• C. Two
• D. Three

Answer 1

The correct option is A Zero

We know that half life for $n^{th}$ order reaction $\propto [A{]}^{1-n}$

For $n=0$,
$t_{1/2}\propto [A{]}^1$
Hence, as the initial concentration increases, the half life increases. We can also say that as the initial concentratin decreases, the half life decreases proportionally.