The effect of absorption of `CO_(2)` gas on acidity of water is explained by following three equilibrium reactions.
`CO_(2)gArrCO_(2(aq))`
`CO_(2(aq))+H_(2)OhArrH_(aq)^(+)+HCO_(3(aq))^(-)`
`HCO_(3(aq))^(-)+H_(2)OhArrH_(3)O_(aq)^(+)+CO_(3)^(2-)`
Which of the following will increase the solubility of `CO_(2)` gas in water?

Options

A. increasing the temperature
B. increasing partial pressure of `CO_(2)` above water
C. addig `HNO_(3)` in water
D. Adding sodium acetate in water.

Explanation

To determine which factor will increase the solubility of CO₂ gas in water, we can analyze the given equilibrium reactions and apply Le Chatelier's principle.

### Step-by-Step Solution:

1. **Understanding the Equilibrium Reactions**:
- The first reaction shows the dissolution of CO₂ gas into aqueous CO₂:
\[ CO_2(g) \rightleftharpoons CO_2(aq) \]
- The second reaction shows the formation of carbonic acid (H₂CO₃) from dissolved CO₂ and water:
\[ CO_2(aq) + H_2O \rightleftharpoons H^+(aq) + HCO_3^-(aq) \]
- The third reaction shows the further dissociation of bicarbonate into carbonate ions:
\[ HCO_3^-(aq) + H_2O \rightleftharpoons H_3O^+(aq) + CO_3^{2-}(aq) \]

2. **Identifying Factors Affecting Solubility**:
- According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid. This means that increasing the pressure of CO₂ will increase its solubility in water.
- Temperature also affects solubility; generally, for gases, increasing temperature decreases solubility.

3. **Applying Le Chatelier's Principle**:
- If we increase the pressure of CO₂, the equilibrium will shift to the right (toward the formation of more CO₂ in aqueous form), thus increasing the solubility of CO₂.

4. **Evaluating the Options**:
- **Increasing Temperature**: This would decrease the solubility of CO₂ (not correct).
- **Increasing Partial Pressure of CO₂**: This will increase the solubility of CO₂ (correct).
- **Adding Ashenothrein to Water**: This is not a known factor affecting CO₂ solubility (not correct).
- **Adding Sodium Acetate**: This does not directly influence the solubility of CO₂ (not correct).

5. **Conclusion**:
- The correct answer is **increasing the partial pressure of CO₂ above water**.

### Final Answer:
The factor that will increase the solubility of CO₂ gas in water is **increasing the partial pressure of CO₂ above water**.