Which of the following is a characteristic of covalent compounds? MCQ with Answer and Explanation

Explanation:
Froth flotation is used for sulphide ores (ZnS, PbS, CuFeS₂). Ore particles adhere to oil froth and float, gangue sinks. Magnetic separation for magnetic ores. Calcination and smelting are extraction steps, not concentration.

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:
According to Charles's Law (V ∝ T), extrapolating the volume-temperature graph of an ideal gas to absolute zero (0 K) yields a volume of zero. At 0 K, the theoretical kinetic energy of molecules is zero, meaning they stop moving. Both are true, but the zero volume is a mathematical extrapolation of the gas law, not a direct physical consequence of zero kinetic energy alone, as real gases liquefy first.