In acidic medium, the rate of reaction between $$\left[ {BrO_3^ - } \right]$$ and $$\left[ {B{r^ - }} \right]$$ ions is given by the expression $$ - \frac{{d\left[ {BrO_3^ - } \right]}}{{dt}}$$ $$ = k\left[ {BrO_3^ - } \right]\left[ {B{r^ - }} \right]{\left[ {{H^ + }} \right]^2}$$
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 :
Only (iii) and (iv)
Solution :
(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 $$ \propto {\left[ {{H^ + }} \right]^2}.$$
Releted MCQ Question on Physical Chemistry >> Chemical Kinetics
Releted Question 1
If uranium (mass number 238 and atomic number 92) emits an $$\alpha $$ -particle, the product has mass no. and atomic no.