Answer : The value of [tex]K'_c[/tex] for the reaction is, 7.5
Explanation :
Initial concentration of [tex]N_2O_4[/tex] = [tex]\frac{Moles}{Volume}=\frac{0.625}{5}=0.125M[/tex]
The balanced decomposition equilibrium reaction is,
            [tex]N_2O_4(g)\rightleftharpoons 2NO_2(g)[/tex]
Initial conc. Â Â 0.125 Â Â Â Â Â 0
At eqm. Â Â Â Â Â (0.125-x) Â Â Â 2x
The expression of equilibrium constant for the reaction will be:
[tex]K_c=\frac{[NO_2]^2}{[N_2O_4]}[/tex]
Now put all the values in this expression, we get :
[tex]K_c=\frac{(2x)^2}{(0.125-x)}[/tex]
The concentration of [tex]N_2O4[/tex] at equilibrium = 0.0750 M
So, 0.125 - x = 0.0750
x = 0.05 M
Now put the value of 'x' in the above expression, we get:
[tex]K_c=\frac{(2\times 0.05)^2}{(0.0750)}[/tex]
[tex]K_c=0.133[/tex]
Now we have to calculate the value of [tex]K_c[/tex] for the given reaction.
[tex]2NO_2(g)\rightleftharpoons N_2O_4(g)[/tex] Â [tex]K'_c[/tex]
As we know that,
[tex]K'_c=\frac{1}{K_c}[/tex]
So,
[tex]K'_c=\frac{1}{0.133}[/tex]
[tex]K'_c=7.5[/tex]
Therefore, the value of [tex]K'_c[/tex] for the reaction is, 7.5