A catalyst lowers the activation energy of a reaction. This results in: MCQ with Answer and Explanation

Explanation:
Boyle's law: P₁V₁ = P₂V₂. Given P₁=1.0 atm, V₁=2.0 L, P₂=4.0 atm. V₂ = (1.0 × 2.0) / 4.0 = 0.5 L. Volume decreases as pressure increases, because gas is compressible. The product PV is constant for a fixed mass of gas at constant T. Scuba divers experience this; as they dive deeper, pressure increases, reducing air volume in lungs.

Explanation:
Hydrogen has ~150 kJ/g; LPG ~50 kJ/g; CNG ~55 kJ/g; diesel ~45 kJ/g. Hydrogen has highest energy per mass but low density, posing storage challenges.

Explanation:
Contact process: SO₂ + O₂ ⇌ SO₃ (catalyst V₂O₅) followed by absorption in H₂SO₄ to produce H₂S₂O₇, then H₂SO₄.