JEE Main · 2023 · 10 Apr 2023 · Shift 2 · Chemical Kinetics

For a zero-order reaction $t_{1/2}=\frac{[A{]}_0}{2k}$, so as $[A{]}_0$ falls the successive half-lives shorten; statement A is correct. A reactant to which the rate is zero order does not change the rate when its concentration varies, so statement B is correct. Order can be fractional, but molecularity counts the species meeting in one elementary step and must be a whole number, so statement C is wrong. For a zero-order reaction $k$ has units $\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$ and for a second-order reaction $k$ has units $\mathrm{mo}{\mathrm{l}}^{-1}\mathrm{L}{\mathrm{s}}^{-1}$, so statement D is correct. The number of incorrect statements is 1.