When electrolysis is carried out on water, __________ gas is liberated at the anode.

Options

A. Hydrogen
B. Oxygen
C. Nitrogen
D. Ozone

Answer

To solve the question "When electrolysis is carried out on water, __________ gas is liberated at the anode," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electrolysis**: Electrolysis is a process that uses electric current to drive a chemical reaction. In the case of water (H2O), when electrolysis is performed, it breaks down into its constituent ions.

2. **Identifying Electrodes**: In an electrolytic cell, there are two electrodes: the anode and the cathode. The anode is connected to the positive terminal of the battery, while the cathode is connected to the negative terminal.

3. **Dissociation of Water**: When electric current passes through water, it dissociates into hydroxide ions (OH⁻) and hydrogen ions (H⁺). The reaction can be represented as:
\[ H_2O \rightarrow H^+ + OH^- \]

4. **Movement of Ions**: The H⁺ ions (which are positively charged) move towards the cathode (negative electrode), while the OH⁻ ions (which are negatively charged) move towards the anode (positive electrode).

5. **Reaction at the Anode**: At the anode, the hydroxide ions (OH⁻) give up their electrons. The reaction that occurs at the anode can be represented as:
\[ 4OH^- \rightarrow O_2 + 2H_2O + 4e^- \]
This reaction produces oxygen gas (O₂).

6. **Conclusion**: Therefore, when electrolysis is carried out on water, oxygen gas is liberated at the anode.

### Final Answer:
Oxygen gas is liberated at the anode during the electrolysis of water.

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