Step 1: Analyze the properties of CO2 and H2 gases Carbon dioxide (CO
2) is a colourless gas that can dissolve in water to form carbonic acid (H
2CO
3).
Hydrogen gas (H
2) is also colourless and is typically found in its molecular form as a gas.
Step 2: Evaluate the options - Option (1): Soluble in water: While both gases are soluble in water, this is not their most defining property.
- Option (2): Colourless: Both CO2 and H2 gases are colourless, which is the most accurate and defining property in this case.
- Option (3): Acidic: CO2 is acidic when dissolved in water, but this property does not apply to hydrogen gas, which is neutral.
- Option (4): Heavier than air: CO2 is heavier than air, but hydrogen is lighter than air, making this option incorrect.
Step 3: Conclusion The most accurate description of both gases is that they are colourless.
Conclusion: Both gases are colourless.