Identify the incorrect statement regarding chemical equilibrium

Options

A. It can be attained from either side.
B. `Q_(c)=K_(c)` at equilibrium.
C. Equilibrium is achieved when the reactant and product concentrations become equal.
D. Presence of catalyst influences the position of equilibrium

Answer

To identify the incorrect statement regarding chemical equilibrium, let's analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement:** Chemical equilibrium can be attained from either side.

**Explanation:** This statement is true. In a reversible reaction, the reactants can form products, and the products can also revert back to reactants. Therefore, equilibrium can be achieved from either direction.

**Hint:** Remember that reversible reactions can proceed in both forward and backward directions.

### Step 2: Analyze the Second Statement
**Statement:** \( Q_c \) is equal to \( K_c \) at equilibrium.

**Explanation:** This statement is also true. At equilibrium, the reaction quotient (\( Q_c \)) becomes equal to the equilibrium constant (\( K_c \)). This means that the concentrations of the reactants and products remain constant over time.

**Hint:** Recall that \( Q_c \) represents the ratio of the concentrations of products to reactants at any point, while \( K_c \) is specifically at equilibrium.

### Step 3: Analyze the Third Statement
**Statement:** Equilibrium is achieved when the reactant and product concentrations become equal.

**Explanation:** This statement is incorrect. Equilibrium does not necessarily mean that the concentrations of reactants and products are equal. Instead, it means that the rates of the forward and reverse reactions are equal. The concentrations can be different depending on the reaction.

**Hint:** Focus on the concept that equilibrium is about the rates of reactions being equal, not the concentrations.

### Step 4: Analyze the Fourth Statement
**Statement:** The presence of a catalyst influences the position of equilibrium.

**Explanation:** This statement is true. A catalyst speeds up both the forward and reverse reactions equally, allowing the system to reach equilibrium faster, but it does not change the position of equilibrium itself.

**Hint:** Remember that catalysts affect the rate of reaching equilibrium but do not affect the equilibrium concentrations.

### Conclusion
The incorrect statement regarding chemical equilibrium is the third statement: "Equilibrium is achieved when the reactant and product concentrations become equal."