Question

The correct difference between first and second order reactions is that

• A. A first-order reaction can catalyze; a second-order reaction cannot be catalyzed
• B. 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 $[A{]}_0$
• C. 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
• D. 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

Answer 1

Answer: (B)

For first order reaction, $t_{1/2}=\frac{0.693}{k},$ which is independent of initial concentration of reactant. $(t_{1/2}\cancel{\propto }a)$
For second order reaction, $t_{1/2}=\frac{1}{k[A_0]},$ which depends on initial concentration of reactant $\left(t_{1/2}\propto \frac{1}{a}\right)$