In a vessel containing `N_(2),H_(2)` and `NH_(3)` at equilibrium , some helium gas is introduced so that total pressure increase while temperature and volume remain constant .According to Le Chatelier's principle , the dissociation of `NH_(3)`:

Options

A. Increases
B. decreases
C. remains unltered
D. changes unpredictably

Answer

To solve the problem regarding the dissociation of ammonia (NH₃) in the presence of an inert gas (helium) at equilibrium, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the System**:
- We have a chemical equilibrium involving nitrogen (N₂), hydrogen (H₂), and ammonia (NH₃).
- The equilibrium reaction can be represented as:
\[ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \]

2. **Introduction of Helium Gas**:
- Helium gas, which is an inert gas, is introduced into the system.
- The introduction of helium increases the total pressure in the vessel.

3. **Constant Temperature and Volume**:
- It is specified that the temperature and volume of the system remain constant.
- This is crucial because it affects how the system responds to changes in pressure.

4. **Applying Le Chatelier's Principle**:
- Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in conditions (such as concentration, temperature, or pressure), the system will adjust to counteract that change and restore a new equilibrium.
- However, the addition of an inert gas at constant volume does not change the partial pressures of the reactants and products involved in the equilibrium reaction.

5. **Effect of Inert Gas on Equilibrium**:
- Since helium does not react with any of the components in the equilibrium and does not change the partial pressures of N₂, H₂, or NH₃, the equilibrium position remains unchanged.
- Therefore, the dissociation of ammonia (NH₃) will not be affected by the addition of helium gas.

6. **Conclusion**:
- The dissociation of ammonia remains unaltered despite the increase in total pressure due to the addition of helium gas.

### Final Answer:
According to Le Chatelier's principle, the dissociation of ammonia (NH₃) will not be affected by the introduction of helium gas at constant temperature and volume.

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