The chief ore of iron is: MCQ with Answer and Explanation

Explanation:
Aluminium oxide (Al₂O₃) reacts with both acids and bases, so it is amphoteric. Na₂O and MgO are basic; CuO is basic. ZnO is also amphoteric.

Explanation:
Ionic character increases with the difference in electronegativity between bonding atoms. In hydrogen halides, electronegativity decreases from F to I (F: 4.0, Cl: 3.0, Br: 2.8, I: 2.5). Thus HF has the largest electronegativity difference (1.9) and highest ionic character. The trend: HF > HCl > HBr > HI. However, HF is still a covalent polar molecule. Exam tip: Electronegativity difference > 1.7 usually indicates ionic bond.

Explanation:
Soda-lime glass is produced by fusing silica (SiO₂) with sodium carbonate (Na₂CO₃) and calcium carbonate (CaCO₃) at high temperature. Na₂CO₃ acts as flux to lower melting point, CaCO₃ provides stability. Reaction: Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂. Sodium chloride is not used. Potassium compounds make harder glass.