Concept:According to Le Chatelier's Principle, adding more reactant to a system at equilibrium throws the system out of balance, forcing it to consume the excess.
Formula:$$ Q_c = \frac{[\text{NO}_2]^2}{[\text{N}_2\text{O}_4]} $$
Solution:- By adding \( \text{N}_2\text{O}_4 \), you spike the concentration of the reactant (the denominator in the \( Q_c \) expression).
- This makes \( Q_c < K_c \). The system is no longer at equilibrium.
- To restore equilibrium, the system must reduce the denominator and increase the numerator by converting the excess \( \text{N}_2\text{O}_4 \) into \( \text{NO}_2 \).
- This direction (left to right) is known as the forward reaction.
Why other options are incorrect:Starting the reverse reaction would require adding product. It heavily disturbs equilibrium. Temperature changes are external stresses, not guaranteed products of this specific physical addition.
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