When aqueous solution of KCl is electrolysed, resultant solution has

Options

A. `pH gt 7`
B. `pH lt 7`
C. `pH = 7`
D. Initially less than 7 then increases

Answer

To solve the question regarding the electrolysis of an aqueous solution of KCl, we will analyze the reactions occurring at both the cathode and anode during the process.

### Step-by-Step Solution:

1. **Understanding Electrolysis**:
- Electrolysis involves the breakdown of an electrolyte (in this case, KCl) into its constituent ions when an electric current is passed through it.

2. **Dissociation of KCl in Water**:
- When KCl is dissolved in water, it dissociates into potassium ions (K⁺) and chloride ions (Cl⁻):
\[ \text{KCl (aq)} \rightarrow \text{K}^+ (aq) + \text{Cl}^- (aq) \]

3. **Identifying Reactions at the Cathode**:
- At the cathode, reduction occurs. The possible species that can be reduced are K⁺ and water (H₂O).
- The standard reduction potential (SRP) for K⁺ is very low compared to that of water. Therefore, water will be reduced instead of K⁺:
\[ 2 \text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 (g) + 2 \text{OH}^- (aq) \]
- This reaction produces hydrogen gas (H₂) and hydroxide ions (OH⁻).

4. **Identifying Reactions at the Anode**:
- At the anode, oxidation occurs. The possible species that can be oxidized are Cl⁻ and water.
- Chloride ions (Cl⁻) have a higher tendency to be oxidized compared to water. Therefore, the oxidation of Cl⁻ occurs:
\[ 2 \text{Cl}^- \rightarrow \text{Cl}_2 (g) + 2e^- \]
- This reaction produces chlorine gas (Cl₂).

5. **Resultant Solution**:
- The electrolysis of KCl results in the formation of hydrogen gas at the cathode and chlorine gas at the anode.
- The hydroxide ions produced at the cathode increase the pH of the solution, making it basic.
- The overall reaction can be summarized as:
\[ 2 \text{H}_2\text{O} \rightarrow \text{H}_2 (g) + 2 \text{OH}^- (aq) \quad \text{(at cathode)} \]
\[ 2 \text{Cl}^- \rightarrow \text{Cl}_2 (g) + 2e^- \quad \text{(at anode)} \]

6. **Conclusion**:
- The resultant solution after the electrolysis of aqueous KCl will contain hydroxide ions (OH⁻), which makes the solution basic, and the gases H₂ and Cl₂ will be evolved.