In electrolysis of water ______ gas is liberated at cathode.

Explanation

To answer the question, "In electrolysis of water, ______ gas is liberated at cathode," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electrolysis**:
- Electrolysis is a process that uses electricity to break down a compound into its elements. In this case, we are looking at water (H₂O).

2. **Components of Water**:
- Water is made up of two hydrogen atoms and one oxygen atom (H₂O).

3. **Electrolysis Setup**:
- During electrolysis, water is placed in an electrolytic cell, which consists of two electrodes: an anode (positive electrode) and a cathode (negative electrode).

4. **Current Flow**:
- When an electric current is passed through the water, it causes the water molecules to decompose into hydrogen and oxygen gases.

5. **Gas Production**:
- At the cathode (the negative electrode), reduction occurs. This means that hydrogen ions (H⁺) gain electrons to form hydrogen gas (H₂).
- At the anode (the positive electrode), oxidation occurs, producing oxygen gas (O₂).

6. **Conclusion**:
- Therefore, the gas that is liberated at the cathode during the electrolysis of water is hydrogen gas (H₂).

### Final Answer:
In electrolysis of water, **hydrogen gas** is liberated at the cathode.

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