The hypothetical reaction $${A_2} + {B_2} \to 2AB;$$ follows the following mechanism \[{{A}_{2}}\xrightarrow{\text{Fast}}A+A,\] \[A+{{B}_{2}}\xrightarrow{\text{Slow}}AB+B,A+B\xrightarrow{\text{Fast}}AB\cdot \]
The order of the overall reaction is
A.
$$0$$
B.
$$1$$
C.
$$2$$
D.
$$\frac{3}{2}$$
Answer :
$$\frac{3}{2}$$
Solution :
$$\eqalign{
& {A_2} + {B_2} \to 2AB; \cr
& {A_2} \to A + A\left( {{\text{Fast}}} \right) \cr
& A + {B_2} \to AB + B\left( {{\text{Slow}}} \right) \cr} $$
Rate law $$ = k\left[ A \right]\left[ {{B_2}} \right]$$ put value of $$\left[ A \right]$$ from $${{\text{I}}^{{\text{st}}}}$$ reaction since $$A$$ is intermediate $$\sqrt {k\left[ {{A_2}} \right]} = A$$
∴ Rate law equation $$ = K\sqrt {k\left[ {{A_2}} \right]} \left[ {{B_2}} \right]$$
∴ Order $$ = \frac{1}{2} + 1 = \frac{3}{2}$$
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.