Question

In the reaction, $2 NO + Cl _{2} \rightarrow 2 NOCl$, it has been found that doubling the concentration of both the reactants increases the rate by a factor of eight but doubling the chlorine concentration alone only doubles the rate. Which of the following statements is incorrect?

• A. The reaction is first order in $Cl _{2}$.
• B. The reaction is second order in NO.
• C. The overall order of reaction is 2 .
• D. The overall order of reaction is $3 $

Answer 1

Answer: (C)

(i) $r=k[ NO ]^{\alpha}\left[ Cl _{2}\right]^{\beta}=k a^{\alpha} b^{\beta}$

(ii) $8 r=k(2 a)^{\alpha}(2 b)^{\beta}$

(iii) $2 r=k a^{\alpha}(2 b)^{\beta}$

Dividing (ii) by (iii), $4=2^{\alpha}$ or $\alpha=2$

Dividing (iii) by (i), $2=2^{\beta}$ or $\beta=1$

Overall order $=2+1=3$