Assertion (A): Covalent compounds generally have low melting points. Reason (R): The intermolecular forces in covalent compounds are weak compared to ionic compounds. MCQ with Answer and Explanation

Explanation:
Stainless steel is an alloy of iron with chromium (minimum 10.5%), often nickel, and sometimes molybdenum. Chromium forms a passive oxide layer (Cr₂O₃) that prevents rusting. Brass is Cu + Zn. Bronze is Cu + Sn. Solder is Pb + Sn. Stainless steel is used in kitchen utensils, surgical instruments, and architecture. The most common type is 304 stainless (18% Cr, 8% Ni).

Explanation:
Zymase, a complex of enzymes from yeast, catalyzes fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. Invertase hydrolyzes sucrose; urease hydrolyzes urea; maltase converts maltose to glucose.

Explanation:
Magnesium oxide (MgO) is a basic oxide because it reacts with acids to form salt and water, e.g., MgO + 2HCl → MgCl₂ + H₂O. However, Reason is false: Metals generally form basic oxides, not acidic oxides. Non-metals form acidic oxides (e.g., SO₂, CO₂). Some metals like Al, Zn form amphoteric oxides. So A is true, R false. Exam tip: Metal oxides are usually basic; non-metal oxides are acidic.