Heating a II group metal carbonate leads to decomposition as :
`BaCO_(3)(s)hArrBaO(s)+CO_(2)(g)`
Equilibrium will shift left

Options

A. by addition of BaO (s)
B. by addition of `CO_(2)(g)`
C. by decreasing the temperature
D. by decreasing the volume of the vessel

Answer

To solve the question regarding the decomposition of barium carbonate (BaCO₃) and the conditions under which the equilibrium shifts to the left, we will analyze the reaction and apply Le Chatelier's principle step by step.

### Step-by-Step Solution:

1. **Write the Decomposition Reaction**:
The decomposition of barium carbonate can be represented as:
\[ \text{BaCO}_3(s) \rightleftharpoons \text{BaO}(s) + \text{CO}_2(g) \]
This reaction indicates that solid barium carbonate decomposes into solid barium oxide and gaseous carbon dioxide.

2. **Understand the Concept of Equilibrium**:
In this reaction, an equilibrium is established between the reactants (BaCO₃) and the products (BaO and CO₂). The position of this equilibrium can be affected by changes in concentration, pressure, and temperature.

3. **Analyze the Effects of Adding Barium Oxide**:
- When barium oxide (BaO), which is a solid, is added to the system, it does not affect the equilibrium position because the concentration of pure solids does not change the equilibrium state.
- **Conclusion**: Adding BaO does not shift the equilibrium.

4. **Analyze the Effects of Adding Carbon Dioxide**:
- If carbon dioxide gas is added to the system, the concentration of CO₂ increases.
- According to Le Chatelier's principle, the system will respond by shifting the equilibrium to the left to reduce the concentration of CO₂.
- **Conclusion**: Adding CO₂ shifts the equilibrium to the left.

5. **Analyze the Effects of Decreasing Temperature**:
- The decomposition of barium carbonate is an endothermic reaction (it requires heat).
- If the temperature is decreased, the equilibrium will shift to favor the exothermic direction (the reverse reaction) to produce more BaCO₃.
- **Conclusion**: Decreasing the temperature shifts the equilibrium to the left.

6. **Analyze the Effects of Decreasing the Volume of the Vessel**:
- Decreasing the volume of the vessel increases the pressure of the system.
- Since the only gas present is CO₂, an increase in pressure will shift the equilibrium towards the side with fewer moles of gas.
- In this case, the left side (reactants) has no gas, while the right side has 1 mole of CO₂ gas. Thus, the equilibrium will shift to the left to reduce pressure.
- **Conclusion**: Decreasing the volume shifts the equilibrium to the left.

### Final Conclusion:
From the analysis:
- Adding BaO does not shift the equilibrium.
- Adding CO₂, decreasing temperature, and decreasing volume all shift the equilibrium to the left.

### Correct Options:
- The conditions that shift the equilibrium to the left are:
- B: By addition of carbon dioxide gas.
- C: By decreasing the temperature.
- D: By decreasing the volume of the vessel.