Question

For the reaction; $2 NO + Br _{2} \rightleftharpoons 2 NOBr$
the mechanism is given in two steps
a: $NO + Br _{2} \stackrel{\text{ Fast} } {\rightleftharpoons} NOBr _{2}$
b. $NOBr _{2}+ NO \stackrel{\text { Slow }}{\longrightarrow } 2 NOBr$
The rate expression for the reaction is

• A. $r=K[N O]^{2}\left[B r_{2}\right]$
• B. $r=K[ NO ]\left[ Br _{2}\right]$
• C. $r=K[NO ]\left[B r_{2}\right]^{2}$
• D. $r=K\left[N O B r_{2}\right]$

Answer 1

Answer: (A)

rate $= k \left[ NOBr _{2}\right][ NO ]$

Also $k_{c}=\frac{\left[N O B r_{2}\right]}{[N O]\left[B r_{2}\right]}$

$\left[ NOBr _{2}\right]= k _{c}[ NO ]\left[ Br _{2}\right]$

$=k'\,\,\, k_{c}[N O]\left[B r_{2}\right][N O]$

$= k [ NO ]^{2}\left[ Br _{2}\right]$