The nitrate ion can be converted into ammonium ion. The equivalent mass of `NO_(3)^(-)` ion in this reaction would be :

Options

A. 6.20 g
B. 7.75 g
C. 10.5 g
D. 21.0 g

Answer

To find the equivalent mass of the nitrate ion (NO₃⁻) when it is converted into ammonium ion (NH₄⁺), we will follow these steps:

### Step 1: Identify the oxidation states
- **Nitrate ion (NO₃⁻)**: The oxidation state of nitrogen (N) in NO₃⁻ can be calculated as follows:
Let the oxidation state of nitrogen be \( x \).
\[ x + 3(-2) = -1 \quad \text{(since the overall charge is -1)} \]
\[ x - 6 = -1 \implies x = +5 \]
So, the oxidation state of nitrogen in NO₃⁻ is +5.

- **Ammonium ion (NH₄⁺)**: The oxidation state of nitrogen in NH₄⁺ can be calculated similarly:
Let the oxidation state of nitrogen be \( y \).
\[ y + 4(-1) = +1 \quad \text{(since the overall charge is +1)} \]
\[ y - 4 = +1 \implies y = -3 \]
So, the oxidation state of nitrogen in NH₄⁺ is -3.

### Step 2: Calculate the change in oxidation state
- The change in oxidation state (Δx) when converting from NO₃⁻ to NH₄⁺ is:
\[ \Delta x = \text{Final oxidation state} - \text{Initial oxidation state} = (-3) - (+5) = -8 \]
Taking the absolute value, we have:
\[ |\Delta x| = 8 \]

### Step 3: Calculate the equivalent mass
- The equivalent mass of a substance is given by the formula:
\[ \text{Equivalent mass} = \frac{\text{Gram molecular mass (GMM)}}{n} \]
where \( n \) is the number of electrons transferred (which is equal to Δx in this case).

- The gram molecular mass (GMM) of the nitrate ion (NO₃⁻) is 62 g/mol.

- Substituting the values into the formula:
\[ \text{Equivalent mass} = \frac{62 \, \text{g/mol}}{8} = 7.75 \, \text{g/equiv} \]

### Final Answer
The equivalent mass of the nitrate ion (NO₃⁻) in this reaction is **7.75 g/equiv**.

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