Question

Diazonium salt decomposes as $C_{6}H_{5}N_{2}^{+}Cl^{-}\to C_{6}H_{5}Cl+N_{2}$. At $0^{\circ}C$ the evolution of$N_2$ becomes two times faster when the initial concentration of the salt is doubled. Therefore, it is

• A. A first order reaction
• B. A second order reaction
• C. Independent of the initial concentration of the salt
• D. A zero order reaction

Answer 1

Answer: (A)

For reaction $C_{6}H_{5}N_{2}^{+}Cl^{-}\to C_{6}H_{5}Cl+N_{2}$
Let the rate law be $r=\frac{d\left[N_{2}\right]}{dt}=k\left[C_{6}H_{5}N^{+}_{2}Cl^{-}\right]^{x} $
$=k\left[Salt\right]^{x} ....\left(i\right)$
From given, if $2r=\frac{2d\left[N_{2}\right]}{dt}=k\left(2\left[salt\right]\right)^{x} ...\left(ii\right)$
Then, on dividing$\left(i\right)$ by $\left(ii\right)$ we get
$\frac{1}{2}=\left(\frac{1}{2}\right)^{x} \Rightarrow x=1$
$\therefore $ Reaction is of 1st order