Question

Half-life of a chemical reaction at a given concentration is 50 minutes. When the concentration of the reactant is doubled, the half-life becomes 100 minutes. The order of the reaction is:

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

Answer 1

Answer: (A)

Step 1:
Half life $\propto [A{]}^{1-n}$
$T_1=50min$ when concentration is $x$
$T_2=100min$ when concentration is $2x$

Step 2:
$\frac{T_1}{T_2}=\frac{x^{1-n}}{(2x{)}^{1-n}}$
$\frac{50}{100}=(\frac{1}{2}{)}^{1-n}$
$n=0$

Hence, option (A) is correct.