Question

The following mechanism has been proposed for the reaction of NO with Br2 to form NOBr.

NO (g) + Br2 (g) $\rightleftharpoons$NOBr2 (g) ;NOBr2 (g) + NO (g) $\longrightarrow$ 2NOBr (g) (slow step)

If the second step is the rate determining step, the order of the reaction with respect to NO(g) is

• A. 1
• B. 0
• C. 3
• D. 2

Answer 1

Answer: (D)

2

Answer 2

$\text{NO}(g)\text{ + B}\text{r}_{2}(g)$ $\rightleftharpoons$ $\text{NOB}\text{r}_{2}(g)$ NOBr2 (g)

$\longrightarrow$+ NO (g) 2NOBr (g) [rate determining step]

Rate of the reaction (r) = k [NOBr2] [NO]

where$\lbrack\text{NOB}\text{r}_{2}\rbrack\text{ = }\text{K}_{c}\ \lbrack\text{NO}\rbrack\ \lbrack\text{B}\text{r}_{2}\rbrack r = k.K_{C}.\lbrack NO\rbrack\left\lbrack Br_{2} \right\rbrack\lbrack NO\rbrack\text{r = k' }\lbrack\text{NO}\rbrack^{2}\ \lbrack\text{B}\text{r}_{2}\rbrack.$

The order of the reaction with respect to NO(g) = 2.