For the reaction below, the partial pressure of [tex]$NO_2$[/tex] is 0.30 bar and the partial pressure of [tex]$N_2O_4$[/tex] is 1.0 bar. What is the Q of the reaction? [tex]$R = 0.08314 \, L \cdot bar / mol \cdot K; K_p = 0.25$[/tex]

[tex]\[
2 NO_2(g) \rightleftharpoons N_2O_4(g)
\][/tex]



Answer :

To determine the reaction quotient (Q) for the given chemical equilibrium, we need to use the partial pressures of the reactants and products. The reaction in question is:

[tex]\[ 2 \, \text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g) \][/tex]

Given:
- Partial pressure of NO[tex]\(_2\)[/tex] is 0.30 bar.
- Partial pressure of N[tex]\(_2\)[/tex]O[tex]\(_4\)[/tex] is 1.0 bar.
- The equilibrium constant [tex]\(K_p\)[/tex] is 0.25.

Firstly, let's recall the formula for the reaction quotient [tex]\(Q\)[/tex]. For the general reaction:

[tex]\[ aA(g) + bB(g) \rightleftharpoons cC(g) + dD(g) \][/tex]

The reaction quotient [tex]\(Q\)[/tex] is given by:

[tex]\[ Q = \frac{(\text{partial pressure of } C)^c \cdot (\text{partial pressure of } D)^d}{(\text{partial pressure of } A)^a \cdot (\text{partial pressure of } B)^b} \][/tex]

For our specific reaction:

[tex]\[ 2 \, \text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g) \][/tex]

The reaction quotient [tex]\(Q\)[/tex] becomes:

[tex]\[ Q = \frac{(\text{partial pressure of } N_2O_4)}{(\text{partial pressure of } NO_2)^2} \][/tex]

Now, substituting the given values:

Partial pressure of NO[tex]\(_2\)[/tex] = 0.30 bar
Partial pressure of N[tex]\(_2\)[/tex]O[tex]\(_4\)[/tex] = 1.0 bar

[tex]\[ Q = \frac{1.0 \, \text{bar}}{(0.30 \, \text{bar})^2} \][/tex]

[tex]\( (0.30 \, \text{bar})^2 = 0.09 \, \text{bar}^2 \)[/tex]

Thus,

[tex]\[ Q = \frac{1.0 \, \text{bar}}{0.09 \, \text{bar}^2} \][/tex]

[tex]\[ Q = 11.1111 \][/tex]

Therefore, the reaction quotient [tex]\(Q\)[/tex] for the reaction is [tex]\( 11.1111 \)[/tex].