Question

For the reaction:

$3Cl{O}^{-}\to Cl{O}_3^{-}+2C{l}^{-}$

Mechanism:

$Cl{O}^{-}+Cl{O}^{-}\to Cl{O}_2^{-}+C{l}^{-}----\left(slow\right)$

$Cl{O}_2^{-}+Cl{O}^{-}\to Cl{O}_3^{-}+C{l}^{-}-----\left(fast\right)$

The rate of reaction of given reaction is given by ___________.

• A. $K_1[Cl{O}^{-}{]}^3$
• B. $K_1[Cl{O}^{-}{]}^2$
• C. $K_1\left[Cl{O}_2^{-}\right]$
• D. $K_1[Cl{O}^{-}{]}^0$

Answer 1

The correct option is B $K_1[Cl{O}^{-}{]}^2$

The rate of the reaction is proportional to the concentration of the reactants raised to a power. The power is given by the order of the reaction. The rate constant is given by $k$.

The reaction takes place in a two-step.

$Cl{O}^{-}+Cl{O}^{-}\to Cl{O}_2-+C{l}^{-}\left(slow\right)$

$Cl{O}_2^{-}+Cl{O}^{-}\to Cl{O}_3^{-}+C{l}^{-}\left(fast\right)$

Here slow step is a rate-determining step and there are two reactant molecules.

Let $K_1$ and $K_2$ be the rate constant of the first and second steps.

The rate of reaction only depends upon the number of reactant in the rate-determining step.

Thus, rate of reaction $=K_1[Cl{O}^{-}{]}^2$