The equilibrium,` BaCO_3(s) hArr Ba0(s) + CO_2(g)` will shift in left hand direction by

Options

A. Addition of BaO(s)
B. Removal of CO_2(g)
C. Removal of Bao(s)
D. Decreasing the volume of the vessel

Answer

To determine the conditions under which the equilibrium reaction

\[ \text{BaCO}_3(s) \rightleftharpoons \text{BaO}(s) + \text{CO}_2(g) \]

will shift to the left (favoring the formation of BaCO3), we can analyze the factors that affect the equilibrium position according to Le Chatelier's principle.

### Step-by-Step Solution:

1. **Identify the Reaction Components**:
- The reaction involves solid barium carbonate (BaCO3) dissociating into solid barium oxide (BaO) and carbon dioxide gas (CO2).

2. **Understand the Direction of Shift**:
- A leftward shift indicates that the formation of reactants (BaCO3) is favored over the products (BaO and CO2).

3. **Factors Affecting Equilibrium**:
- According to Le Chatelier's principle, 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.

4. **Increase in Product Concentration**:
- To shift the equilibrium to the left, we can increase the concentration of the products (BaO and CO2). This can be achieved by adding more BaO or CO2 to the system.

5. **Evaluate the Options**:
- If we add BaO, the concentration of the product increases, which will shift the equilibrium to the left.
- Removing CO2 would decrease the concentration of a product, leading to a shift to the right, which is not what we want.
- Removing BaO would also decrease the concentration of a product, leading to a shift to the right.
- Changing the volume of the vessel does not directly affect the concentration of solids and thus does not influence the equilibrium in this case.

6. **Conclusion**:
- The correct condition to shift the equilibrium to the left is to **add BaO**.

### Final Answer:
The equilibrium will shift to the left by the addition of BaO.