Question

The half-life period for the catalytic decomposition of $A{B}_3\left(g\right)$ at 50 mm initial pressure is 4 hrs and at 100 mm initial pressure it is 2 hrs. The order of the reaction is:

• A. 0
• B. 1
• C. 2
• D. 3

Answer 1

The correct option is C 2

Formula for half life

$t_{1/2}=\frac{1}{|A_0{|}^{n-1}}$

$\frac{(t_{1/2}{)}_1}{(t_{1/2}{)}_2}$=$\frac{{\left[A_0\right]}_2^{n-1}}{{\left[A_0\right]}_1^{n-1}}$

$\frac{4}{2}={\left(\frac{100}{50}\right)}^{n-1}$

$n=2$