For the gas phase reaction `2SO_2 +O_2 hArr 2SO_3, DeltaH=-x` carried out in a vesssel, the equilibrium concentration of `SO_2` can be increased by

Options

A. increasing the temperature
B. decreasing the pressure
C. removing some oxygen
D. none of the above

Answer

To solve the problem regarding the gas phase reaction \(2SO_2 + O_2 \rightleftharpoons 2SO_3\) with \(\Delta H = -x\), we need to determine how to increase the equilibrium concentration of \(SO_2\).

### Step-by-Step Solution:

1. **Understand the Reaction**:
The given reaction is an exothermic reaction, as indicated by the negative \(\Delta H\). This means that heat is released when the reaction proceeds to the right (towards the formation of \(SO_3\)).

2. **Le Chatelier's Principle**:
According to Le Chatelier's Principle, if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium.

3. **Option 1 - Increasing Temperature**:
- Increasing the temperature adds heat to the system.
- Since the reaction is exothermic, the system will respond by shifting the equilibrium to the left (towards the reactants) to absorb the excess heat.
- This shift will increase the concentration of \(SO_2\).

4. **Option 2 - Decreasing Pressure**:
- Decreasing the pressure will increase the volume of the system.
- The reaction has 3 moles of gas on the left (2 moles of \(SO_2\) and 1 mole of \(O_2\)) and 2 moles of gas on the right (2 moles of \(SO_3\)).
- According to Le Chatelier's Principle, the equilibrium will shift towards the side with more moles of gas to counteract the decrease in pressure.
- Therefore, the equilibrium will shift to the left, increasing the concentration of \(SO_2\).

5. **Option 3 - Removing Oxygen**:
- Removing \(O_2\) decreases the concentration of one of the reactants.
- To counteract this change, the equilibrium will shift to the left to produce more \(O_2\).
- This shift will also increase the concentration of \(SO_2\).

6. **Conclusion**:
All three options (increasing temperature, decreasing pressure, and removing oxygen) will lead to an increase in the equilibrium concentration of \(SO_2\).

### Final Answer:
The equilibrium concentration of \(SO_2\) can be increased by:
- Increasing the temperature.
- Decreasing the pressure.
- Removing some oxygen.