Potassium (K) is an alkali metal placed at the very top of the reactivity series. It reacts violently with water and air, requiring storage in kerosene. Gold, silver, and copper are noble or less reactive metals placed at the bottom of the series, often found in the free state.
Explanation:
Bauxite (Al₂O₃·2H₂O) is the primary ore of aluminum. Haematite (Fe₂O₃) is an ore of iron. Cinnabar (HgS) is an ore of mercury, and Galena (PbS) is an ore of lead. Bauxite is purified to alumina before being electrolyzed to extract pure aluminum metal.
Explanation:
Salt is obtained by evaporation of seawater in shallow ponds. Water evaporates leaving salt behind. Filtration cannot separate dissolved salt. Distillation would give pure water, not salt. Sublimation for sublimable solids.
Explanation:
Rusting involves anodic oxidation of iron (Fe → Fe²⁺ + 2e⁻) and cathodic reduction of oxygen (O₂ + 2H₂O + 4e⁻ → 4OH⁻) in the presence of water acting as electrolyte. CO₂ can form carbonic acid accelerating it, but not required. Nitrogen is inert. High temperature alone doesn't cause rusting without moisture and oxygen.
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