Answer
Since $Q_c \gt K_c$, the mixture is not at equilibrium, and the reaction will proceed in the reverse direction, toward reactants.
Work Step by Step
1. Calculate all the concentrations:
$$[N_2O_4] = ( 0.0205 )/(5.25) = 0.00390 M$$
$$[NO_2] = ( 0.750 )/(5.25) = 0.143 M$$
- The exponent of each concentration is equal to its balance coefficient.
$$Q_c = \frac{[Products]}{[Reactants]} = \frac{[ NO_2 ] ^{ 2 }}{[ N_2O_4 ]}$$
2. Substitute the values and calculate the quocient value:
$$Q_c = \frac{( 0.143 )^{ 2 }}{( 0.00390 )} = 5.20$$
Since $Q_c \gt K_c$, the mixture is not at equilibrium, and the reaction will proceed in the reverse direction, toward reactants.