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 determine the resultant pH of an aqueous solution of KCl after electrolysis, we can analyze the reactions occurring at the electrodes during the process. Here’s a step-by-step solution:

### Step 1: Understand the Electrolysis of KCl
When an aqueous solution of potassium chloride (KCl) is electrolyzed, it dissociates into potassium ions (K⁺) and chloride ions (Cl⁻) in water. The water also dissociates into hydrogen ions (H⁺) and hydroxide ions (OH⁻).

**Hint:** Remember that during electrolysis, ions migrate towards the electrodes where reduction and oxidation reactions occur.

### Step 2: Identify Reactions at the Cathode
At the cathode, reduction occurs. The possible species that can be reduced are K⁺ and H₂O. However, the reduction potential of K⁺ is very low, meaning it is less likely to be reduced compared to water.

**Hint:** Compare the standard reduction potentials of the species involved to determine which will be reduced.

### Step 3: Determine the Reduction Reaction
Since water has a higher reduction potential than K⁺, water will be reduced at the cathode. The reduction reaction can be represented as:
\[ 2H_2O + 2e^- \rightarrow H_2 + 2OH^- \]
This reaction produces hydroxide ions (OH⁻).

**Hint:** Focus on the products formed during the reduction process to understand how they affect pH.

### Step 4: Identify Reactions at the Anode
At the anode, oxidation occurs. The possible species that can be oxidized are Cl⁻ and water. Chloride ions can be oxidized to chlorine gas (Cl₂), and water can be oxidized to oxygen gas (O₂). However, the oxidation of Cl⁻ to Cl₂ is more favorable under typical conditions.

**Hint:** Consider the products formed at the anode and their implications for the overall reaction.

### Step 5: Analyze the Effect on pH
The production of OH⁻ ions at the cathode will increase the basicity of the solution, leading to an increase in pH. Initially, the pH of the KCl solution is neutral (around 7), but as OH⁻ ions are generated, the pH will rise above 7.

**Hint:** Remember that an increase in hydroxide ions corresponds to an increase in pH, indicating a more basic solution.

### Conclusion
After the electrolysis of an aqueous solution of KCl, the resultant solution will have a pH greater than 7 due to the formation of hydroxide ions (OH⁻) at the cathode.

**Final Answer:** The resultant solution has a pH greater than 7.

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