Question

The correct difference between first- and second-order reactions is that

• A. the rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations
• B. the rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
• C. a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed
• D. the half-life of a first-order reaction does not depend on $[A{]}_0$; the half-life of a second-order reaction does depend on $[A{]}_0$

Answer 1

Answer: (D)

♦ For first order reaction, $t_{1/2}=\frac{0.693}{k}$,

which is independent of initial concentration of reactant.

♦ For second order reaction, $t_{1/2}=\frac{1}{k\left[A_0\right]}$,

which depends on initial concentration of reactant.