Global warming is caused by the trapping of: MCQ with Answer and Explanation

Explanation:
Plaster of Paris is calcium sulfate hemihydrate, CaSO₄·½H₂O. It is obtained by heating gypsum (CaSO₄·2H₂O) at 373 K. It sets to a hard mass on mixing with water reforming gypsum. Option B (2CaSO₄·H₂O) is equivalent to CaSO₄·½H₂O but the conventional representation is CaSO₄·½H₂O. Option A is gypsum, D is anhydrous calcium sulfate. POP is used for making casts, statues, and as a building material.

Explanation:
In reaction C, H₂O₂ oxidizes PbS (black) to PbSO₄ (white), where oxygen atoms from H₂O₂ are added. H₂O₂ itself is reduced to H₂O. In reaction D, H₂O₂ oxidizes I⁻ to I₂; that is also oxidation. But the most straightforward oxidizing reaction among these is the restoration of old paintings (PbS → PbSO₄). Reaction A: H₂O₂ reduces O₃ (acts as reducing agent). Reaction B: H₂O₂ reduces Ag₂O. H₂O₂ can act as both oxidizing and reducing agent.

Explanation:
Calorific value is the amount of heat energy produced on the complete combustion of 1 kg (or 1 m³ for gases) of a fuel. It is expressed in kJ/kg or kJ/m³. Hydrogen has the highest calorific value among common fuels, making it a highly efficient energy source.