A substance having very high vapour pressure at its melting point on heating will show_______________?
Correct answer: B. Sublimation
- A. Melting
- B. Sublimation
- C. Decomposition
- D. Condensation
Explanation
A substance with very high vapour pressure can pass directly from solid to vapour when heated, provided its vapour pressure exceeds the surrounding pressure. This direct solid-to-gas change is sublimation. The common trap is melting, which requires the solid to form a liquid first.
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About Evaporation, Boiling Point and Vapour Pressure
Evaporation is the escape of higher-energy molecules from a liquid surface, while vapour pressure is the pressure exerted by vapour in equilibrium with that liquid. The topic distinguishes evaporation from boiling and relates both to temperature, intermolecular forces, surface area, atmospheric pressure and the boiling point.
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