Which non-metal is a good conductor of electricity?
A. Phosphorus
B. Graphite
C. Iodine
D. Sulphur
Answer: Option B
Solution (By JKExamLibrary)
Graphite, an allotrope of carbon, is a good conductor of electricity. This is because each carbon atom is bonded to three others, leaving one free valence electron per atom that is delocalized and can move freely between the layers to conduct electricity, unlike diamond which is an insulator.
Explanation:
Boiling water changes state from liquid to gas, but the chemical composition (H₂O) remains unchanged – physical change. Others form new substances.
Explanation:
A bomb calorimeter burns a known mass of fuel in excess oxygen inside a sealed bomb immersed in water. The temperature rise of water is measured to calculate heat released. Thermometer is part of it but not the device itself.
Explanation:
NaOH is a strong base, fully dissociating into Na⁺ and OH⁻ ions. NH₄OH is a weak base. Ca(OH)₂ and Mg(OH)₂ are sparingly soluble but are considered strong bases in terms of dissociation of dissolved portion, but NaOH is the strongest among common ones.
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