In a vessel `N_(2),H_(2)andNH_(3)` are at equilibrium. Some helium gas is introduction into the vessel so that total pressure increases while temperature and volume remain constant. According to Le Chatelier's principle, the dissociation of `NH_(3)`

Options

A. increases
B. decreases
C. remains unchanged
D. equilibrium is disturbed.

Explanation

To solve the question regarding the effect of introducing helium gas into a vessel containing nitrogen (N₂), hydrogen (H₂), and ammonia (NH₃) at equilibrium, we can follow these steps:

### Step 1: Understand the Equilibrium Reaction
The equilibrium reaction for the synthesis of ammonia is:
\[ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \]

### Step 2: Identify the Changes Made
In this scenario, helium gas (an inert gas) is introduced into the vessel. It is important to note that the volume of the vessel remains constant, and the temperature is also constant.

### Step 3: Apply Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust to counteract that change and restore a new equilibrium.

### Step 4: Analyze the Effect of Adding an Inert Gas
When an inert gas like helium is added to the system at constant volume:
- The total pressure of the system increases due to the addition of the inert gas.
- However, the partial pressures of the reactants (N₂ and H₂) and the product (NH₃) do not change because the volume is constant.

### Step 5: Conclusion
Since the partial pressures of the gases involved in the equilibrium do not change, the equilibrium position remains unaffected. Therefore, the dissociation of NH₃ remains unchanged.

### Final Answer
The dissociation of NH₃ remains unchanged.