Question

At $300\,K$ the half‐life a sample of a gaseous compound initially at $1atm$ is $100\sec$ . When the pressure is $0.5\,atm$ the half‐life is $50\sec$ . The order of reaction is

Answer 1

For a zero order reaciton,
$t_{1 / 2} \propto$ initial concentration
$\Rightarrow t _{1 / 2} \propto$ pressure
Since, half life decreases to half with similar
decrease in pressure. Hence, the order of
reaction is zero.