For the reaction $2 \mathrm{H}_{2}(\mathrm{~g})+2 \mathrm{NO}(\mathrm{g}) \rightarrow \mathrm{N}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})$ the observed rate expression is, rate $=\mathrm{k}_{\mathrm{f}}[\mathrm{NO}]^{2}\left[\mathrm{H}_{2}\right]$. The rate expression for the reverse reaction is:
Correct Option: , 4
Rate of forward reaction $=\mathrm{k}_{\mathrm{f}}[\mathrm{NO}]^{2}\left[\mathrm{H}_{2}\right]^{2}$
Observed rate $=\mathrm{k}_{\mathrm{f}}[\mathrm{NO}]^{2}\left[\mathrm{H}_{2}\right]$
Observed rate $=\frac{\text { Rate of forward reaction }}{\left[\mathrm{H}_{2}\right]}$
$\therefore$ Rate of backward reaction $=\frac{k_{b}\left[\mathrm{~N}_{2}\right]\left[\mathrm{H}_{2} \mathrm{O}\right]^{2}}{\left[\mathrm{H}_{2}\right]}$