In order to mention the boiling point of water at 110°C the external pressure should be ?
Correct answer: A. Between 760 torr and 1200 torr
- A. Between 760 torr and 1200 torr
- B. Between 200 torr and 760 torr
- C. 765 torr
- D. any value of pressure
Explanation
Water boils when its vapour pressure equals the external pressure. Since water's vapour pressure at 110°C is greater than 760 torr and is approximately within 760 to 1200 torr, the external pressure must lie in that range. Students may choose 765 torr by thinking the pressure only needs to be slightly above normal atmospheric pressure.
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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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