Which of the following is considered the cleanest fuel?
A. Coal
B. Hydrogen
C. Wood
D. Diesel
Answer: Option B
Solution (By JKSSB Mock Tests)
Hydrogen is considered the cleanest fuel because its combustion produces only water (2H₂ + O₂ → 2H₂O) and no greenhouse gases or toxic pollutants. Coal, wood, and diesel produce CO₂, CO, SO₂, and particulate matter, contributing significantly to air pollution and global warming.
Explanation:
Tritium (³H) is a radioactive isotope with a half-life of ~12.3 years, decaying by beta emission to ³He. Protium (¹H) and deuterium (²H) are stable. Tritium is used in self-luminous paints, tracer studies, and nuclear fusion. It occurs naturally in very small amounts from cosmic rays but is mainly produced in nuclear reactors.
Explanation:
Temporary hardness is due to dissolved bicarbonates of Ca and Mg. These can be removed by boiling, which precipitates carbonates. Calcium sulfate and chloride cause permanent hardness. Sodium chloride does not cause hardness. Boiling: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂. Bicarbonates are formed when water containing CO₂ passes over limestone.
Explanation:
Chemical bonds are attractive forces between atoms due to electron interaction—ionic (transfer), covalent (sharing), metallic, etc. These bonds hold atoms together in molecules or crystals. Nuclear force holds protons and neutrons in nucleus. Gravitational and magnetic forces are negligible at atomic scale. Bond energy determines stability; stronger bond means more energy required to break.
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