The chemical process used for extracting a metal from its ore by dissolving it in a suitable reagent is called:
A. Smelting
B. Calcination
C. Leaching
D. Roasting
Answer: Option C
Solution (By JKSSB Mock Tests)
Leaching is a chemical method of concentration where the powdered ore is treated with a suitable reagent that dissolves the ore but not the impurities. Calcination and roasting are thermal processes, and smelting involves reduction with a chemical reducing agent like carbon at high temperatures.
Explanation:
Primary batteries are non-rechargeable; the chemical reaction that produces electricity cannot be reversed. The common dry cell (zinc-carbon battery) and alkaline batteries are primary cells. Lead-acid, Ni-Cd, and Li-ion are secondary (rechargeable) batteries where the reaction can be reversed by applying an external current.
Explanation:
H₂O₂ decomposes when exposed to light (photochemical decomposition): 2H₂O₂ → 2H₂O + O₂. Light provides energy to break the O–O bond. To prevent decomposition, it is stored in amber or opaque bottles, often with stabilizers like urea or phosphoric acid. Also, traces of heavy metal ions catalyze decomposition. H₂O₂ is a strong oxidizing agent and bleaching agent.
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.
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