Ionic product of water increases, if

Options

A. `H^+` ions are added
B. OH ions are added
C. Temperature decreases
D. Temperature increases

Answer

To solve the question regarding the conditions under which the ionic product of water (Kw) increases, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Ionic Product of Water**:
The ionic product of water (Kw) is defined as the product of the concentrations of hydrogen ions (H⁺) and hydroxide ions (OH⁻) in pure water at a given temperature. Mathematically, it is expressed as:
\[ K_w = [H^+][OH^-] \]

2. **Consider the Factors Affecting Kw**:
The ionic product of water can be influenced by several factors, including the concentration of H⁺ and OH⁻ ions, and temperature.

3. **Analyze Each Option**:
- **Option 1: Adding H⁺ ions**:
When H⁺ ions are added, the equilibrium shifts according to Le Chatelier's principle, favoring the reverse reaction (formation of water), which decreases the dissociation of water. Thus, Kw does not increase.

- **Option 2: Adding OH⁻ ions**:
Similarly, adding OH⁻ ions also shifts the equilibrium to the left, reducing the dissociation of water. Therefore, Kw does not increase.

- **Option 3: Decreasing Temperature**:
Lowering the temperature generally favors the exothermic direction of the dissociation of water, which would also not increase Kw.

- **Option 4: Increasing Temperature**:
Increasing the temperature promotes the endothermic dissociation of water, leading to an increase in the concentrations of H⁺ and OH⁻ ions. Consequently, Kw increases.

4. **Conclusion**:
The only condition under which the ionic product of water increases is when the temperature is increased. Thus, the correct answer is:
\[ \text{The ionic product of water increases if the temperature is increased.} \]

### Final Answer:
The ionic product of water increases if the temperature is increased.

---