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:** "Equilibrium can be attained from either side."

**Explanation:** This statement is true. Chemical equilibrium can indeed be reached from the reactant side (A + B) or the product side (C + D). The equilibrium is established when the rate of the forward reaction equals the rate of the backward reaction.

### Step 2: Analyze the second statement
**Statement:** "Qc is equal to Kc at equilibrium."

**Explanation:** This statement is also true. The reaction quotient (Qc) represents the ratio of the concentrations of products to reactants at any point in time. At equilibrium, Qc equals the equilibrium constant (Kc), indicating that the system is at a stable state.

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

**Explanation:** This statement is incorrect. Equilibrium is not defined by the concentrations of reactants and products being equal. Instead, it is achieved when the rate of the forward reaction equals the rate of the backward reaction. The concentrations of reactants and products can be different at equilibrium.

### Step 4: Analyze the fourth statement
**Statement:** "Presence of a catalyst influences the position of the equilibrium."

**Explanation:** This statement is true. While a catalyst does not change the equilibrium constant or the position of equilibrium, it does speed up the rate at which equilibrium is reached. It affects the rates of both the forward and backward reactions equally.

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