Molarity of a given orthophosphoric acid solution is 3M. Its normality is

Options

A. 9N
B. 0.3 N
C. 3N
D. 1 N

Answer

To find the normality of a 3M orthophosphoric acid (H₃PO₄) solution, we can follow these steps:

### Step 1: Understand the Definitions
- **Molarity (M)** is defined as the number of moles of solute per liter of solution.
- **Normality (N)** is defined as the number of gram equivalents of solute per liter of solution.

### Step 2: Identify the n Factor
- The n factor for an acid is the number of protons (H⁺ ions) that can be donated by one molecule of the acid.
- For orthophosphoric acid (H₃PO₄), it can donate 3 protons (H⁺ ions) when dissolved in water.

### Step 3: Relate Normality and Molarity
- The relationship between normality and molarity can be expressed with the formula:
\[ \text{Normality (N)} = \text{Molarity (M)} \times n \text{ factor} \]

### Step 4: Substitute the Values
- Given that the molarity (M) is 3M and the n factor for H₃PO₄ is 3, we can substitute these values into the formula:
\[ \text{Normality (N)} = 3 \, \text{M} \times 3 = 9 \, \text{N} \]

### Step 5: Conclusion
- Therefore, the normality of the orthophosphoric acid solution is **9N**.