The process of obtaining a metal from its ore by heating with a reducing agent is called:
A. Roasting
B. Calcination
C. Smelting
D. Leaching
Answer: Option C
Solution (By JKExamLibrary)
Smelting involves heating the concentrated ore (often after roasting/calcination) with a reducing agent (like coke, CO) to reduce the metal oxide to the metal. For example, iron ore is smelted in a blast furnace. Roasting heats sulfide ores in air; calcination heats carbonate ores in absence of air; leaching dissolves out the metal.
Explanation:
White phosphorus exists as P₄ tetrahedral molecules, containing 4 phosphorus atoms. So atomicity is 4. Sulfur is S₈, oxygen is O₂, ozone O₃. Atomicity is the number of atoms in a molecule of an element. Phosphorus is a non-metal. Red phosphorus is polymeric but P₄ is the common molecular form.
Explanation:
Ice (solid H₂O) is a molecular solid where molecules are held together by hydrogen bonds and van der Waals forces. Diamond is a covalent network solid. NaCl is ionic solid. Iron is metallic solid. Molecular solids have low melting points, are soft, and are poor conductors. Other examples: dry ice (CO₂), iodine, sugar.
Explanation:
Lead-acid batteries use dilute sulfuric acid (approx 35%). During discharge, H₂SO₄ concentration decreases, forming PbSO₄ on both electrodes.
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