One mole of magnesium nitride on reaction with an excess of water gives

Options

A. one mole of `NH_(3)`
B. two moles of `NH_(3)`
C. one mole of `HNO_(3)`
D. two moles of `HNO_(3)`

Explanation

To solve the problem of what one mole of magnesium nitride (Mg3N2) produces when it reacts with an excess of water, we can follow these steps:

### Step 1: Write the Chemical Reaction
Magnesium nitride reacts with water to produce magnesium hydroxide and ammonia. The unbalanced equation is:
\[ \text{Mg}_3\text{N}_2 + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2 + \text{NH}_3 \]

### Step 2: Identify the Products
From the reaction, we know the products are magnesium hydroxide (Mg(OH)2) and ammonia (NH3).

### Step 3: Balance the Reaction
To balance the reaction, we need to ensure that the number of atoms of each element is the same on both sides of the equation.

1. **Magnesium (Mg)**: There are 3 magnesium atoms in Mg3N2, so we need 3 Mg(OH)2:
\[ \text{Mg}_3\text{N}_2 + \text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + \text{NH}_3 \]

2. **Nitrogen (N)**: There are 2 nitrogen atoms in Mg3N2, so we need 2 NH3:
\[ \text{Mg}_3\text{N}_2 + \text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + 2\text{NH}_3 \]

3. **Oxygen (O) and Hydrogen (H)**: Now we need to balance the water. Each Mg(OH)2 has 2 hydroxide ions, so for 3 Mg(OH)2, we have 6 hydroxide ions. This means we need 6 water molecules:
\[ \text{Mg}_3\text{N}_2 + 6\text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + 2\text{NH}_3 \]

### Step 4: Count the Moles of Products
From the balanced equation, we see that:
- 3 moles of magnesium hydroxide (Mg(OH)2) are produced.
- 2 moles of ammonia (NH3) are produced.

### Conclusion
Therefore, when one mole of magnesium nitride reacts with an excess of water, it produces 2 moles of ammonia (NH3).

### Final Answer
**2 moles of NH3**

---