On dissolving 1 mole of each of the following acids in 1 litre water, the acid which does not give a solution of strength 1N is -

Options

A. HCl
B. `HClO_(4)`
C. `HNO_(3)`
D. `H_(3) PO_(4)`

Answer

To determine which acid does not give a solution of strength 1N when 1 mole is dissolved in 1 liter of water, we need to analyze the normality of each acid based on its dissociation and the number of replaceable hydrogen ions (H⁺ ions) it provides.

### Step-by-Step Solution:

1. **Understanding Normality**:
Normality (N) is defined as the number of equivalents of solute per liter of solution. For acids, the number of equivalents is determined by the number of replaceable H⁺ ions (basicity).

2. **Identify the Acids**:
We need to consider the acids given in the options. Let's assume the acids are:
- HCl (Hydrochloric acid)
- HNO₃ (Nitric acid)
- HClO₄ (Perchloric acid)
- H₃PO₄ (Phosphoric acid)

3. **Determine the Basicity (n factor)**:
- For **HCl**: It dissociates to give 1 H⁺ ion. Therefore, n factor = 1.
- For **HNO₃**: It also dissociates to give 1 H⁺ ion. Therefore, n factor = 1.
- For **HClO₄**: It dissociates to give 1 H⁺ ion. Therefore, n factor = 1.
- For **H₃PO₄**: It can dissociate to give 3 H⁺ ions (H₃PO₄ → 3H⁺ + PO₄³⁻). Therefore, n factor = 3.

4. **Calculate Normality**:
- For HCl, HNO₃, and HClO₄:
- Molarity = 1 mole in 1 liter = 1 M
- Normality = Molarity × n factor = 1 M × 1 = 1 N
- For H₃PO₄:
- Molarity = 1 mole in 1 liter = 1 M
- Normality = Molarity × n factor = 1 M × 3 = 3 N

5. **Conclusion**:
The acid that does not yield a solution of strength 1N is **H₃PO₄** (Phosphoric acid) because it has a higher n factor of 3, resulting in a normality of 3N instead of 1N.

### Final Answer:
The acid which does not give a solution of strength 1N is **H₃PO₄** (Phosphoric acid).