Question

A reaction with reaction quotient $Q_C$ and equilibrium constant $K_C$ will proceed in the direction of the products when:

• A. $Q_C = K_C$
• B. $Q_C>K_C$
• C. $Q_C<K_C$
• D. $Q_C = 0$

Hint:

If $Q_C<K_C$, reactant concentrations are too high relative to products—so the reaction moves forward to make more products.

Answer 1

The Correct Option is C

The reaction quotient $Q_C$ compares the current ratio of product and reactant concentrations to the equilibrium constant $K_C$. \[ \begin{cases} Q_C<K_C & \text{means the reaction shifts toward products to reach equilibrium},\\ Q_C = K_C & \text{means the system is at equilibrium},\\ Q_C>K_C & \text{means the reaction shifts toward reactants}. \end{cases} \] Since $Q_C<K_C$, more products will form until $Q_C$ rises to equal $K_C$.

• (A) $Q_C = K_C$ — no net reaction (at equilibrium) — incorrect.
• (B) $Q_C>K_C$ — reaction shifts left (toward reactants) — incorrect.
• (C) $Q_C<K_C$ — reaction shifts right (toward products) — correct.
• (D) $Q_C = 0$ — an extreme case of (C), but general condition is $Q_C<K_C$ — incomplete.