Question

For the reaction, $2 NO + Cl _{2} \longrightarrow 2 NOCl$ The following mechanism has been proposed
$NO +\rightleftharpoons NOCl _{2} \text { (fast) }$
$NOCl _{2}+ NO \longrightarrow 2 NOCl \text { (slow) }$

• A. Rate $= k [ NO ]\left[ Cl _{2}\right]^{2}$
• B. Rate $= k [ NO ]^{2}\left[ Cl _{2}\right]$
• C. Rate $= k [ NOCl ]^{2}$
• D. Rate $= k \left[ NOCl _{2}\right][ NO ]$

Answer 1

Answer: (B)

From slow step,
Rate $= k \left[ NOCl _{2}\right][ NO ]\,\,\,$ (i)
From fast step
Equation constant $K =\frac{\left[ NOCl _{2}\right]}{[ NO ]\left[ CL _{2}\right]}$
Putting the value of $\left[ NOCl _{2}\right]$ in (i)
Rate $= Kk'[ NO ]^{2}\left[ Cl _{2}\right]$
Rate $= k [ NO ]^{2}[ Cl ]$