The process of converting a concentrated ore into its oxide by heating in excess air is:
A. Calcination
B. Smelting
C. Refining
D. Roasting
Answer: Option D
Solution (By JKExamLibrary)
Roasting is the process of heating the concentrated ore (usually sulfide ores) strongly in the presence of excess air below its melting point. It converts the ore to its oxide form and removes volatile impurities as gases (e.g., 2ZnS + 3O₂ → 2ZnO + 2SO₂).
Explanation:
Niels Bohr in 1913 proposed the planetary model where electrons revolve in certain allowed circular orbits without radiating energy, with quantized angular momentum. Rutherford proposed the nuclear model but did not specify quantized orbits. Thomson gave plum pudding. Chadwick discovered neutron.
Explanation:
BOD stands for Biological Oxygen Demand. It is a measure of the amount of dissolved oxygen required by microorganisms to decompose the organic matter present in a water sample. High BOD indicates severe organic pollution and poor water quality for aquatic life.
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