Hard water can be softened by adding washing soda because it:
A. Increases pH
B. Precipitates calcium and magnesium ions as carbonates
C. Removes chlorine
D. Kills bacteria
Answer: Option B
Solution (By JKSSB Mock Tests)
Na₂CO₃ reacts with Ca²⁺/Mg²⁺ to form insoluble CaCO₃/MgCO₃, which are removed. This is permanent hardness removal. Boiling works for temporary hardness. Ion exchange is another method.
Explanation:
Permanent hardness is due to CaCl₂, CaSO₄, MgCl₂, MgSO₄. These do not precipitate on boiling. Temporary hardness (bicarbonates) is removed by boiling. Both can be removed by ion exchange or washing soda.
Explanation:
Sulphuric acid (H₂SO₄) was historically called oil of vitriol. Hydrochloric acid was muriatic acid, nitric acid was aqua fortis, carbolic acid is phenol.
Explanation:
Graham's Law of Diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of its density (or molar mass) at constant temperature and pressure (r ∝ 1/√d). Lighter gases diffuse faster than heavier ones, which explains why helium balloons deflate quickly.
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