Hard water contains dissolved salts of calcium and magnesium. Which substance causes temporary hardness?
A. Sodium bicarbonate
B. Calcium bicarbonate
C. Calcium sulfate
D. Magnesium chloride
Answer: Option B
Solution (By JKSSB Mock Tests)
Temporary hardness is due to dissolved bicarbonates of Ca and Mg, which can be removed by boiling: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂. Permanent hardness is caused by chlorides and sulfates of Ca and Mg, not removed by boiling. Sodium bicarbonate does not cause hardness. Methods to remove permanent hardness include treatment with washing soda (Na₂CO₃), ion exchange, or calgon.
Explanation:
Antoine Lavoisier is known as the father of modern chemistry and formulated the law of conservation of mass—mass is neither created nor destroyed in a chemical reaction. Dalton's atomic theory supported this law. Thomson discovered electron. Rutherford discovered nucleus. Lavoisier also named oxygen and hydrogen and established the role of oxygen in combustion.
Explanation:
Nitric acid (HNO3) is historically known as Aqua Fortis, which translates to 'strong water' in Latin. This name was given by early alchemists due to its ability to dissolve almost all metals, including silver, which was not dissolved by other known acids at the time.
Explanation:
V ∝ T (in Kelvin). Using Celsius gives a linear relationship but not direct proportionality (line does not pass through origin). Absolute zero (0 K = -273.15°C) is the theoretical temperature of zero volume.
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