The value of `DeltaH` for the reaction
`X_2(g) +4Y_2(g) hArr 2XY_4(g)`
is less than zero. Formation of `XY_4(g)` will be favoured at

Options

A. High pressure and low temperature
B. High temperature and high pressure
C. low pressure and low temperature
D. High temperature and low pressure

Answer

To determine the conditions under which the formation of \( XY_4(g) \) is favored, we need to analyze the reaction and apply Le Chatelier's Principle. The reaction is:

\[ X_2(g) + 4Y_2(g) \rightleftharpoons 2XY_4(g) \]

Given that the value of \( \Delta H \) for this reaction is less than zero, it indicates that the reaction is exothermic (releases heat).

### Step-by-Step Solution:

1. **Identify the Nature of the Reaction**:
- The reaction is exothermic, meaning it releases heat. Therefore, we can write:
\[ X_2(g) + 4Y_2(g) \rightleftharpoons 2XY_4(g) + \text{heat} \]

2. **Effect of Temperature**:
- According to Le Chatelier's Principle, if we increase the temperature of an exothermic reaction, the equilibrium will shift to the left (towards the reactants) to absorb the excess heat. Conversely, if we decrease the temperature, the equilibrium will shift to the right (towards the products) to produce more heat.
- Thus, to favor the formation of \( XY_4(g) \), we need to maintain a **low temperature**.

3. **Effect of Pressure**:
- Next, we analyze the effect of pressure. The reaction involves:
- Left side: \( 1 + 4 = 5 \) moles of gas (1 mole of \( X_2 \) and 4 moles of \( Y_2 \))
- Right side: \( 2 \) moles of gas (2 moles of \( XY_4 \))
- According to Le Chatelier's Principle, if the pressure is increased, the equilibrium will shift towards the side with fewer moles of gas. Since there are 5 moles on the left and 2 moles on the right, increasing the pressure will favor the formation of \( XY_4(g) \).
- Therefore, we need to maintain a **high pressure**.

### Conclusion:
To favor the formation of \( XY_4(g) \), the conditions should be:
- **Low Temperature**
- **High Pressure**