Question

In acidic medium, the rate of reaction between $[Br{O}_3]$ and $[B{r}^{-}]$ ions is given by the expression
$-\frac{d\left[Br{O}_3^{-}\right]}{dt}=k\left[Br{O}_3^{-}\right]\left[B{r}^{-}\right]{\left[H^{+}\right]}^2$
It means
(i) rate constant of the reaction depends upon the concentration of $H^{+}$ ions
(ii) rate of reaction is independent of the concentration of acid added (iii) the change in $pH$ of the solution will affect the rate of reaction (iv) doubling the concentration of $H^{+}$ ions will increase the reactions rate by 4 times.

• A. Only (ii)
• B. Only (iii)
• C. Only (i) and (ii)
• D. Only (iii) and (iv)

Answer 1

Answer: (D)

(i) is wrong because rate constant does not depend upon the concentrations of the reactants.
(ii) is wrong because rate depends upon ${\left[H^{+}\right]}^2$
(iii) is correct because change in $pH$ means change in$\left[H^{+}\right]$ ions
(iv) is correct because rate $\propto$ ${\left[H^{+}\right]}^2$