On passing electricity through acidulated water, the gaseous products obtained are collected in two separate test tubes A and B. The volume of the gas collected in test tube A is double the volume of gas collected in test tube B. Identify the two gases in test tubes A and B respectively.

Options

A. Hydrogen and oxygen
B. Oxygen and hydrogen
C. Hydrogen peroxide and oxygen
D. Oxygen and water vapour

Explanation

To solve the question about the gases collected in test tubes A and B when electricity is passed through acidulated water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Acidulated Water**:
- Acidulated water is water that has a small amount of acid mixed in it, such as lemon juice or vinegar. This acid helps to conduct electricity when a current is passed through the water.

2. **Electrolysis of Water**:
- When electricity is passed through acidulated water, a process called electrolysis occurs. This process breaks down water (H₂O) into its constituent gases: hydrogen (H₂) and oxygen (O₂).

3. **Gas Production Ratio**:
- The electrolysis of water produces hydrogen gas and oxygen gas in a specific ratio. According to the balanced chemical equation for the electrolysis of water:
\[ 2H₂O \rightarrow 2H₂ + O₂ \]
- This means that for every 2 moles of water, 2 moles of hydrogen gas and 1 mole of oxygen gas are produced. Therefore, the volume of hydrogen gas produced is double that of oxygen gas.

4. **Identifying Gases in Test Tubes**:
- Given that the volume of gas collected in test tube A is double that of test tube B, we can conclude that:
- Test tube A contains hydrogen gas (H₂).
- Test tube B contains oxygen gas (O₂).

5. **Final Identification**:
- Therefore, the gases in the test tubes are:
- Test tube A: Hydrogen (H₂)
- Test tube B: Oxygen (O₂)

### Conclusion:
- The gases collected in the test tubes are:
- Test tube A: Hydrogen (H₂)
- Test tube B: Oxygen (O₂)