On the electrolysis of very dilute aqueous solution of `NaOH` using Pt electrodes

Options

A. `H_2` is evolved at cathode
B. Na is evolved at cathade
C. `Q_2` is evołved at anode
D. `H_(2)` is evolved at anode

Answer

To solve the problem of electrolysis of a very dilute aqueous solution of NaOH using platinum electrodes, we can follow these steps:

### Step 1: Understand the Electrolysis Process
Electrolysis involves the decomposition of a compound in solution by passing an electric current through it. In this case, we are dealing with a dilute aqueous solution of sodium hydroxide (NaOH).

### Step 2: Identify the Electrodes
In this scenario, we are using platinum electrodes. Platinum is an inert electrode, meaning it does not participate in the chemical reactions but serves as a conductor for the electric current.

### Step 3: Determine the Reactions at the Electrodes
During electrolysis, oxidation occurs at the anode and reduction occurs at the cathode.

- **At the Anode:** The hydroxide ions (OH⁻) are oxidized. The reaction can be represented as:
\[ 4OH^{-} \rightarrow 2H_2O + O_2 + 4e^{-} \]
This means that oxygen gas (O₂) is evolved at the anode.

- **At the Cathode:** The hydrogen ions (H⁺) present in the solution are reduced. The reaction can be represented as:
\[ 4H^{+} + 4e^{-} \rightarrow 2H_2 \]
This means that hydrogen gas (H₂) is evolved at the cathode.

### Step 4: Identify the Gases Produced
From the reactions, we can conclude:
- At the cathode, hydrogen gas (H₂) is produced.
- At the anode, oxygen gas (O₂) is produced.

### Step 5: Conclusion
Based on the reactions occurring during the electrolysis of very dilute NaOH solution, we can summarize:
- Hydrogen gas is evolved at the cathode.
- Oxygen gas is evolved at the anode.

### Final Answer
Thus, the correct option is:
- **At cathode: H₂ is evolved; At anode: O₂ is evolved.**