Which of the following factors would favour the formation of ammonia?

Options

A. High pressure
B. Low temperature
C. High volume
D. Low pressure

Explanation

To determine which factors would favor the formation of ammonia (NH3) from nitrogen (N2) and hydrogen (H2), we can analyze the reaction and apply the principles of chemical equilibrium.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The formation of ammonia can be represented by the balanced chemical equation:
\[ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \]

2. **Count the Moles of Gases**:
In the reaction, we have:
- Reactants: 1 mole of N2 and 3 moles of H2, totaling 4 moles of gas.
- Products: 2 moles of NH3.
Thus, the total number of gaseous moles decreases from 4 moles to 2 moles when ammonia is formed.

3. **Apply Le Chatelier's Principle**:
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in pressure, temperature, or concentration, the system will adjust to counteract that change.
- In this case, increasing the pressure will favor the side of the reaction with fewer moles of gas. Since the formation of ammonia results in a decrease in the number of gas moles (from 4 to 2), increasing the pressure will shift the equilibrium towards the right, favoring the formation of ammonia.

4. **Consider Temperature**:
The reaction is exothermic, meaning it releases heat. Generally, lower temperatures favor exothermic reactions, but the question specifically asks about pressure and volume.

5. **Evaluate the Options**:
- **High Pressure**: Favors the formation of ammonia (correct).
- **Low Pressure**: Would not favor the formation of ammonia (incorrect).
- **High Volume**: Would not favor the formation of ammonia as it corresponds to low pressure (incorrect).
- **Low Pressure**: Same as above, would not favor the formation of ammonia (incorrect).

### Conclusion:
The factor that would favor the formation of ammonia is **high pressure**.

### Answer:
High pressure is the correct option.

---