The electrolysis of molten sodium hydride liberates `………………` gas it the `………………`.

Explanation

To solve the question regarding the electrolysis of molten sodium hydride, we can follow these steps:

### Step 1: Understand the Electrolysis Process
Electrolysis involves the decomposition of a compound by passing an electric current through it. In this case, we are dealing with molten sodium hydride (NaH).

**Hint:** Remember that during electrolysis, the compound dissociates into its ions.

### Step 2: Identify the Ions Produced
When sodium hydride is molten, it dissociates into sodium ions (Na⁺) and hydride ions (H⁻).

**Hint:** Look for the ions that will migrate towards the electrodes during electrolysis.

### Step 3: Determine the Reactions at the Electrodes
- **At the Anode (Positive Electrode):** Oxidation occurs. The hydride ions (H⁻) will lose electrons to form hydrogen gas (H₂).

Reaction:
\[ 2H⁻ \rightarrow H₂ + 2e⁻ \]

- **At the Cathode (Negative Electrode):** Reduction occurs. Sodium ions (Na⁺) will gain electrons to form sodium metal (Na).

Reaction:
\[ Na⁺ + e⁻ \rightarrow Na \]

**Hint:** Remember that oxidation occurs at the anode and reduction occurs at the cathode.

### Step 4: Conclude the Products of Electrolysis
From the reactions above, we can conclude that during the electrolysis of molten sodium hydride, hydrogen gas is liberated at the anode, and sodium metal is deposited at the cathode.

**Hint:** Identify the products based on the reactions occurring at each electrode.

### Final Answer
The electrolysis of molten sodium hydride liberates **hydrogen gas** at its **anode**.