Which gas is the main constituent of biogas and natural gas? MCQ with Answer and Explanation

Explanation:
An amalgam is an alloy of mercury with another metal. For example, sodium amalgam (used as reducing agent), zinc amalgam (for Clemmensen reduction), and dental amalgam (mercury-silver-tin-copper). Most metals dissolve in mercury, forming amalgams, except iron and platinum. Amalgams can be liquid or solid depending on proportion. Used in gold extraction.

Explanation:
Urea (CO(NH₂)₂) is a nitrogenous fertilizer with the highest nitrogen content (about 46%). Superphosphate provides phosphorus, muriate of potash (KCl) provides potassium, and gypsum (CaSO₄·2H₂O) is a soil conditioner providing calcium and sulfur, not primary NPK nutrients.

Explanation:
Ozone (O₃) is a powerful disinfectant that decomposes to oxygen, leaving no toxic residues or taste. Chlorination can form carcinogenic trihalomethanes (THMs) with organic matter. However, ozone is more expensive, must be generated on-site, and leaves no residual protection in distribution system, often requiring a small chlorine dose. Ozonation also removes color and odor. Both kill bacteria and viruses.