Sodium hydroxide is produced on a large scale

Options

A. by the hydrolysis of `Na_(2)CO_(3)`
B. by the electrolysis of an aqueous solution of NaCl
C. by adding water to sodium oxide
D. by reacting sodium with water

Answer

To produce sodium hydroxide (NaOH) on a large scale, the Kastner-Kellner process is commonly used. Here is a step-by-step breakdown of the process:

### Step 1: Electrolysis Setup
- The process involves an electrolytic cell known as the Kastner-Kellner cell.
- The cell contains a mercury cathode and a graphite anode.
- An aqueous solution of sodium chloride (NaCl) acts as the electrolyte.

**Hint:** Remember that the electrolytic cell is essential for the electrolysis process, which involves the movement of ions.

### Step 2: Ion Movement
- When an electric current is passed through the NaCl solution, the chloride ions (Cl⁻) migrate towards the anode, while sodium ions (Na⁺) move towards the cathode.

**Hint:** Focus on the movement of ions; Cl⁻ goes to the anode and Na⁺ goes to the cathode.

### Step 3: Reaction at the Anode
- At the graphite anode, chloride ions are oxidized to form chlorine gas (Cl₂) and electrons (e⁻) are released:
\[ 2Cl⁻ \rightarrow Cl₂ + 2e⁻ \]

**Hint:** Oxidation occurs at the anode, leading to the release of chlorine gas.

### Step 4: Reaction at the Cathode
- At the mercury cathode, sodium ions react with the mercury to form sodium amalgam (NaHg):
\[ Na⁺ + e⁻ \rightarrow NaHg \]

**Hint:** The formation of sodium amalgam is a key step that involves sodium ions gaining electrons.

### Step 5: Formation of Sodium Hydroxide
- The sodium amalgam (NaHg) then reacts with water (H₂O) to produce sodium hydroxide (NaOH) and hydrogen gas (H₂):
\[ NaHg + H₂O \rightarrow NaOH + Hg + H₂ \]

**Hint:** This step is crucial as it shows how sodium amalgam is converted into sodium hydroxide and releases hydrogen gas.

### Step 6: Continuous Process
- The process is cyclic, meaning that mercury is recovered and reused, while sodium hydroxide is continuously produced.

**Hint:** The cyclic nature of the process ensures efficiency and sustainability in the production of sodium hydroxide.

### Final Answer
The production of sodium hydroxide is achieved through the electrolysis of an aqueous solution of sodium chloride using the Kastner-Kellner process.

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