JEE Main · 2026 · 02 Apr 2026 · Shift 2 · Chemical Kinetics

The rate constant carries units of $\mathrm{mo}{\mathrm{l}}^{-1}\mathrm{L}{\mathrm{s}}^{-1}$, that is ${\mathrm{M}}^{-1}{\mathrm{s}}^{-1}$, which marks a second-order reaction with rate $=k[X{]}^2$. Raising $[X]$ to four times multiplies the rate by $4^2=16$, so statement A holds and statement B holds. The half-life of a second-order reaction is $t_{1/2}=1/(k[X{]}_0)$, which depends on the initial concentration, so statement C fails. The decomposition of $\mathrm{N}{}_2\mathrm{O}{}_5$ is first order, not second order, so statement D fails, and the linear plot of $\ln ([R{]}_0/[R{]}_t)$ against $t$ belongs to first-order kinetics, so statement E fails. Only statements A and B are correct.