At ${\mathbf{100}}^{\mathbf{\circ }}\mathbf{C}\mathbf{,}\mathbf{}{\mathbf{K}}_{\mathbf{p}}\mathbf{=}\mathbf{60}\mathbf{.}\mathbf{6}$for the reaction

$\mathbf{2}{\mathbf{NOBr}}_{\mathbf{\left(}\mathbf{g}\mathbf{\right)}}\mathbf{\square }\mathbf{}\mathbf{}\mathbf{}\mathbf{2}{\mathbf{NO}}_{\mathbf{\left(}\mathbf{g}\mathbf{\right)}}\mathbf{+}{\mathbf{Br}}_{\mathbf{2}\mathbf{\left(}\mathbf{g}\mathbf{\right)}}$

In a given experiment, 0.10 atm of each component is placed in a container. Is the system at equilibrium? If not, in which direction will the reaction proceed?

Rewrite the reaction as follows:

$2{\mathrm{NOBr}}_{\left(\mathrm{g}\right)}\square 2{\mathrm{NO}}_{\left(\mathrm{g}\right)}+{\mathrm{Br}}_{2\left(\mathrm{g}\right)}$

The expression for the reaction quotient is the ratio of partial pressure of products to partial pressure of reactants, with each partial pressure term raised to a power equal to its stoichiometric coefficient.

The expression for the reaction quotient ${\mathrm{Q}}_{\mathrm{P}}\mathrm{is},$

${\mathrm{Q}}_{\mathrm{P}}=\frac{{\mathrm{P}}^2{}_{\mathrm{NO}}{\mathrm{P}}_{{\mathrm{Br}}_2}}{{\mathrm{P}}^2{}_{\mathrm{NOBr}}}$

The partial pressure of each gas in the reaction is 0.10 atm. That is

role="math" localid="1654920434762" $$\begin{gathered} {\mathrm{P}}_{\mathrm{NO}}={\mathrm{P}}_{{\mathrm{Br}}_2} \\ ={\mathrm{P}}_{\mathrm{NOBr}} \\ =0.10\mathrm{atm} \end{gathered}$$

The value of ${\mathrm{K}}_{\mathrm{P}}$for the reaction at 373 K is 60.6.

If the value of ${\mathrm{Q}}_{\mathrm{P}}$is equal to ${\mathrm{K}}_{\mathrm{P}}$, the reaction will be at equilibrium. Here, ${\mathrm{Q}}_{\mathrm{P}}$is less

than ${\mathrm{K}}_{\mathrm{P}}$.

Thus, the reaction is not at equilibrium.

If the value of ${\mathrm{Q}}_{\mathrm{P}}$is less than ${\mathrm{K}}_{\mathrm{P}}$, the reaction proceeds toward the product’s side to

attain equilibrium. Here ${\mathrm{Q}}_{\mathrm{P}}$is less than ${\mathrm{K}}_{\mathrm{P}}$.

Thus, the reaction shifts towards products.