The reaction quotient, `'Q_c'` in useful in predicting the direction of the reaction. Which of the following is incorrect?

Options

A. If `Q_c gt K_c` , the reverse reaction is favoured
B. If `Q_c lt K_c`, the forward reaction is favoured
C. If `Q_c gt K_c` , forward reaction is favoured.
D. If `Q_c = K_c`, reaction at equillibirium.

Answer

To solve the question regarding the reaction quotient \( Q_c \) and its role in predicting the direction of a chemical reaction, we will analyze the definitions and implications of \( Q_c \) in relation to the equilibrium constant \( K_c \).

### Step-by-Step Solution:

1. **Understanding \( Q_c \)**:
- The reaction quotient \( Q_c \) is defined as the ratio of the concentrations (or partial pressures) of the products to the reactants at any point in time, not necessarily at equilibrium.
- For a general reaction:
\[ aA + bB \rightleftharpoons cC + dD \]
The expression for \( Q_c \) is:
\[ Q_c = \frac{[C]^c[D]^d}{[A]^a[B]^b} \]

2. **Comparing \( Q_c \) and \( K_c \)**:
- The equilibrium constant \( K_c \) is the value of \( Q_c \) when the reaction has reached equilibrium.
- The relationship between \( Q_c \) and \( K_c \) helps in predicting the direction of the reaction:
- If \( Q_c < K_c \): The reaction will proceed in the forward direction (towards products) to reach equilibrium.
- If \( Q_c > K_c \): The reaction will proceed in the reverse direction (towards reactants) to reach equilibrium.
- If \( Q_c = K_c \): The system is at equilibrium, and no net change will occur.

3. **Evaluating the Options**:
- We need to determine which of the statements regarding \( Q_c \) and \( K_c \) is incorrect based on the above understanding.
- The options likely state various scenarios about the relationship between \( Q_c \) and \( K_c \) and the direction of the reaction.

4. **Identifying the Incorrect Statement**:
- By analyzing the possible statements:
- If \( Q_c < K_c \): The reaction goes forward (correct).
- If \( Q_c > K_c \): The reaction goes backward (correct).
- If \( Q_c = K_c \): The reaction is at equilibrium (correct).
- Any statement that contradicts these relationships would be incorrect.

5. **Conclusion**:
- After evaluating the options, the statement that does not align with the principles of \( Q_c \) and \( K_c \) will be identified as the incorrect one.