Temporary hardness of water is caused by bicarbonates. Boiling removes it by converting bicarbonates to:
A. Insoluble carbonates
B. Chlorides
C. Nitrates
D. Sulfates
Answer: Option A
Solution (By JKSSB Mock Tests)
Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂ (on boiling). The precipitate is calcium carbonate. Sulfates and chlorides cause permanent hardness and cannot be removed by boiling.
Explanation:
Natural gas (mainly methane) is a fossil fuel formed from ancient organic matter. Biogas is a renewable fuel from recent organic waste. Hydrogen is an energy carrier, not a fossil fuel. Solar energy is renewable.
Explanation:
Mass number (A) = number of protons (Z) + number of neutrons (N). Electrons have negligible mass and are not counted. It is the total number of nucleons. Example: ¹²C has 6 protons + 6 neutrons = 12. Isotopes have same Z but different A due to varying N. Atomic mass (weight) is the weighted average.
Explanation:
Soap molecules have a hydrophilic ionic head (COO⁻Na⁺) and a long hydrophobic hydrocarbon tail. In water, the tails aggregate away from water, forming a spherical micelle with heads outward. The hydrophobic core dissolves oily dirt, which is then washed away. This structure is stabilized by ion-dipole interactions. Detergents work similarly but with different head groups.
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