Which of the following is not true about a reversible reaction ?

Options

A. (a) The reaction does not proceed to completion.
B. (b) It cannot be influenced by catalyst
C. (c) Number of moles of reactants and products is always equal.
D. (d) It can be attained only in a closed container.

Answer

To determine which statement is not true about a reversible reaction, we will analyze the characteristics of reversible reactions and evaluate each option provided.

### Step-by-Step Solution:

1. **Understanding Reversible Reactions**:
A reversible reaction is one where the reactants can be converted to products and the products can be converted back to reactants. This means that both forward and reverse reactions occur simultaneously.

2. **Equilibrium in Reversible Reactions**:
At equilibrium, the rate of the forward reaction (A to B) is equal to the rate of the reverse reaction (B to A). This does not mean that the concentrations of A and B are equal, but rather that they remain constant over time.

3. **Analyzing the Options**:
- **Option A**: "The reaction does not proceed to completion."
- This statement is true. In a reversible reaction, the reactants and products exist in a dynamic equilibrium, meaning that neither side completely consumes the other.

- **Option B**: "It cannot be influenced by the catalyst."
- This statement is also true. A catalyst speeds up both the forward and reverse reactions equally, thus it does not affect the position of equilibrium.

- **Option C**: "Number of moles of reactants and products are always equal."
- This statement is not true. While the concentrations of reactants and products are constant at equilibrium, the number of moles does not have to be equal. For example, in the reaction A + B ⇌ C, the number of moles of reactants (2) is not equal to the number of moles of products (1).

- **Option D**: "It can be attained only in a closed container."
- This statement is true. Equilibrium can only be established in a closed system where no substances can enter or leave.

4. **Conclusion**:
The statement that is not true about a reversible reaction is **Option C**: "Number of moles of reactants and products are always equal."