O Levels Chemistry (5070)•5070/12/O/N/20
Explanation
Ionic bonds lead to highest melting points among these substances
Steps:
- Classify each substance by bonding type: ammonia and methane are nonpolar/polar molecular, water is polar molecular with hydrogen bonding, sodium chloride is ionic.
- Recall that ionic compounds require more energy to melt due to strong electrostatic attractions between ions.
- Compare approximate melting points: ammonia (-78°C), methane (-182°C), water (0°C), sodium chloride (801°C).
- Identify sodium chloride as having the highest value based on bonding strength.
Why C is correct:
- Sodium chloride is an ionic compound; its high melting point (801°C) follows Coulomb's law, where strong attractions between Na⁺ and Cl⁻ ions demand significant heat to overcome.
Why the others are wrong:
- A. Ammonia: Molecular compound with weak intermolecular forces, melts at -78°C.
- B. Methane: Nonpolar molecular with only London dispersion forces, melts at -182°C.
- D. Water: Polar molecular with hydrogen bonding, but still melts at 0°C, far below ionic solids.
Final answer: C
Topic: Ion and ionic bonds
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