Nitric acid `(70%)` has a specific gravity of `1.42` . Find the normality and molarity of the acid.

Answer

To find the normality and molarity of a 70% nitric acid solution with a specific gravity of 1.42, we can follow these steps:

### Step 1: Understand the Given Information
- **Percentage by weight of nitric acid**: 70%
- **Specific gravity of the solution**: 1.42

### Step 2: Calculate the Density of the Solution
Since specific gravity is the ratio of the density of a substance to the density of water, we can find the density of the nitric acid solution.
- **Density of water**: 1 g/cm³
- **Density of the solution**: Specific gravity × Density of water = 1.42 × 1 g/cm³ = 1.42 g/cm³

### Step 3: Calculate the Molarity
Molarity (M) can be calculated using the formula:
\[ \text{Molarity (M)} = \frac{\text{Percentage by weight} \times \text{Density} \times 10}{\text{Molecular weight}} \]

Where:
- **Percentage by weight** = 70
- **Density** = 1.42 g/cm³
- **Molecular weight of nitric acid (HNO₃)** = 63 g/mol

Substituting the values:
\[ \text{Molarity} = \frac{70 \times 1.42 \times 10}{63} \]
\[ \text{Molarity} = \frac{994}{63} \approx 15.8 \, \text{M} \]

### Step 4: Calculate the Normality
Normality (N) is related to molarity and the valence factor (n) of the acid. For nitric acid, it releases one hydrogen ion (H⁺) per molecule, so the valence factor is 1.
\[ \text{Normality (N)} = \text{Molarity (M)} \times \text{Valence factor} \]
\[ \text{Normality} = 15.8 \, \text{M} \times 1 = 15.8 \, \text{N} \]

### Final Results
- **Molarity of nitric acid**: 15.8 M
- **Normality of nitric acid**: 15.8 N