Question

In acidic medium, the rate of reaction between $[BrO_{3}]$ and $[Br^{-}]$ ions is given by the expression $-\frac{d \left[BrO_{3}^{-}\right]}{d t}=k\left[BrO_{3}^{-}\right]\left[Br^{-}\right]\left[H^{+}\right]^{2}$ 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)

Only (iii) and (iv)

Answer 2

(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 $\propto$ $\left[H^{+}\right]^{2}$