The impurities present in an ore are known as: MCQ with Answer and Explanation

Explanation:
Washing soda (Na₂CO₃) reacts with Ca²⁺ and Mg²⁺ ions in hard water to form insoluble carbonates: Ca²⁺ + Na₂CO₃ → CaCO₃↓ + 2Na⁺. Similarly MgCO₃. These precipitates are removed, softening the water. Ion exchange uses zeolites or resins. Boiling removes only temporary hardness. Distillation is expensive.

Explanation:
Sodium carbonate (Na₂CO₃), also called soda ash, is a key ingredient in glass manufacturing. It lowers the melting point of silica (SiO₂) and provides sodium oxide. The glass batch consists of sand (SiO₂), soda ash (Na₂CO₃), and limestone (CaCO₃). Sodium chloride is table salt, potassium nitrate used in gunpowder, ammonium chloride in batteries/leclanche cells.

Explanation:
Atomic number 8 is oxygen (2,6). It needs 2 more electrons to complete octet, so it gains 2 or shares 2 electrons. Its valency is 2 (typically). It can form two covalent bonds. In H₂O, oxygen forms two bonds.