Which of the following salts is used in fire extinguishers?
A. Potassium nitrate
B. Sodium chloride
C. Calcium sulfate
D. Sodium bicarbonate
Answer: Option D
Solution (By JKSSB Mock Tests)
Sodium bicarbonate (NaHCO₃) is used in soda-acid fire extinguishers. It reacts with sulfuric acid to produce CO₂, which smothers the fire. Also, dry powder extinguishers use NaHCO₃. It is also baking soda.
Explanation:
Phenolphthalein is colorless in acidic and neutral solutions, turning pink/magenta in basic solutions with pH > about 8.2-10. It is commonly used in acid-base titrations. Methyl orange is red in acidic and yellow in basic. Litmus is purple in neutral, red in acid, blue in base. Natural indicators like turmeric, beetroot also show color changes.
Explanation:
In electrolytic refining of copper, the electrolyte is acidified copper sulfate solution (CuSO₄ acidified with H₂SO₄). The anode is impure copper, cathode is pure copper. Cu²⁺ ions from the electrolyte are reduced and deposited on the cathode, while copper from anode oxidizes and enters solution. Impurities settle as anode mud (containing Ag, Au).
Explanation:
Smelting is the pyrometallurgical process of extracting a metal from its ore by heating it beyond its melting point and reducing the metal oxide with a carbonaceous reducing agent (like coke or coal). Flux is often added to remove impurities as slag. Calcination and roasting are oxidation processes.
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