Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium. Boiling precipitates:
A. CaCl₂
B. MgCl₂
C. CaSO₄
D. CaCO₃
Answer: Option D
Solution (By JKExamLibrary)
On boiling, soluble calcium bicarbonate decomposes: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂. The precipitate is calcium carbonate (limestone/chalk). Magnesium bicarbonate similarly forms MgCO₃ or Mg(OH)₂. This removes Ca²⁺ and Mg²⁺ ions, softening the water. Permanent hardness (CaSO₄, CaCl₂) doesn't precipitate on boiling and needs chemical treatment.
Explanation:
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:
Distillation involves boiling and condensation, separating non-volatile impurities (salts) and some volatile impurities. It can also kill microorganisms but boiling already does; distillation purifies further.
Explanation:
Zymase (in yeast) converts sugars to ethanol, catalase (in liver) breaks down hydrogen peroxide, and amylase (in saliva) breaks down starch into sugars. All are biological enzymes that act as highly specific catalysts in biochemical reactions, functioning under mild conditions of temperature and pH.
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