Explanation

• The usual gases used for lifting airships are hydrogen and helium.
• Hydrogen is the lightest known gas and thus has great lifting capacity,
• Helium is not as buoyant but is far safer than hydrogen because it does not burn.

Last verified on 01-04-2026

Explanation

• Natural gas burns with a clean blue flame.
• It indicates complete combustion.
• Blue flame produces more heat and less smoke.
• It is efficient and less polluting.
• Natural gas mainly contains methane (CH₄).

Last verified on 24-05-2026

Explanation

• Effusion is the escape of gas molecules through a tiny hole.
• According to Graham’s law, rate of effusion ∝ 1/√molar mass.
• Lighter gases effuse faster than heavier gases.
• Among given options, hydrogen has the lowest molar mass (H₂ = 2 g/mol).
• Therefore, it moves and escapes the fastest.

Last verified on 19-05-2026

Explanation

• Ozone (O₃) is both beneficial and harmful depending on its location.
• In the Ozone Layer, it protects life by blocking UV rays.
• At ground level, it becomes a pollutant harmful to lungs and plants.
• Thus, it has a dual role in Earth’s atmosphere.

Last verified on 02-05-2026

Explanation

Composition of Air:

• Nitrogen → 78%
• Oxygen → 20.95%
• Argon → 0.93%
• Carbon dioxide → 0.04%
• Other gases → very small traces

Last verified on 30-04-2026