`2SO_(2(g)) + O_(2(g)) hArr 2SO_(3(g)) + Q ` KJ
In the above reaction, how can the yield of product be increased without increasing the pressure ?

Options

A. by increasing temperature
B. by decreasing temperature
C. by increasing th volume of the reaction vessel
D. by the addition of the catalyst

Answer

To increase the yield of the product \( SO_3 \) in the reaction

\[ 2SO_{2(g)} + O_{2(g)} \rightleftharpoons 2SO_{3(g)} + Q \, \text{(heat)} \]

without increasing the pressure, we can follow these steps:

### Step 1: Identify the Nature of the Reaction
This reaction is exothermic, as indicated by the release of heat (Q) during the formation of \( SO_3 \).

**Hint:** Remember that exothermic reactions release heat and the equilibrium shifts in response to temperature changes.

### Step 2: Apply Le Chatelier's Principle
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will adjust to counteract that change and restore a new equilibrium.

**Hint:** Le Chatelier's principle helps predict how changes will affect the position of equilibrium.

### Step 3: Consider Temperature Changes
For exothermic reactions, lowering the temperature shifts the equilibrium to the right (towards the products) to produce more heat. Therefore, decreasing the temperature will favor the formation of \( SO_3 \).

**Hint:** In exothermic reactions, decreasing temperature favors product formation.

### Step 4: Evaluate Other Options
- **Increasing Temperature:** This would shift the equilibrium to the left (towards the reactants), decreasing the yield of \( SO_3 \).
- **Increasing Volume of Reaction Vessel:** This would shift the equilibrium towards the side with more moles of gas (reactants), which is not desired here.
- **Addition of Catalyst:** A catalyst speeds up the rate of reaching equilibrium but does not change the position of equilibrium or the yield of products.

**Hint:** Only changes that affect the equilibrium position will impact the yield of products.

### Conclusion
To increase the yield of \( SO_3 \) without increasing the pressure, the best approach is to **decrease the temperature** of the reaction.

**Final Answer:** Decrease the temperature.