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Q107
(NDA-I/2024)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
Which one among the following oxides has the highest melting point ?
Explanation
The melting point of an oxide is primarily determined by its lattice energy, which depends on the charge of the ions and their ionic radii. According to Coulomb's Law, higher ionic charges and smaller ionic sizes lead to stronger electrostatic forces of attraction, resulting in a higher melting point.
- MgO (Magnesium Oxide): It consists of Mg2+ and O2- ions. The high double charges and relatively small size of the magnesium ion create a very strong ionic bond. Its melting point is approximately 2852°C.
- Na2O: Contains Na+ (single charge), leading to weaker bonds and a melting point of ~1132°C.
- Fe2O3: Has a melting point of approximately 1566°C.
- CuO: Has a melting point of approximately 1326°C.
Because of its exceptionally high thermal stability, MgO is frequently used as a refractory material for lining high-temperature furnaces.
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