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VAPOUR PRESSURE........
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Pressure exerted by the vapour of a liquid at equilibrium is called "Vapour Pressure" of that liquid. OR Pressure exerted by the vapours of a liquid when rate of evaporation is and the rate of condensation becomes equal is called "Vapour Pressure". · Different liquids have different vapor pressure under similar conditions. · Vapour pressure varies with temperature. · At
elevated temperature, vapor pressure also increases |
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| Q) Evaporation is a cooling process, explain. | ||||
| We know that evaporation takes place at all temperatures and pressure. But only those molecules escape from the liquid those high kinetic energies. As a result only those molecules remains that posses low energy. Since K.E is directly related to temperature, we feel a cooling effect due to evaporation. | ||||
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BOILING
POINT
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The temperature at which the vapour pressure of a liquid becomes equal to atmospheric pressure is called BOING PONT. At this temperature a liquid starts boiling. Boiling point of liquid varies with atmospheric pressure. If atmospheric pressure is less then 760 torr then the boiling point of a liquid will decrease from its standard boiling point. Boiling point of a liquid decreases with the decrease in pressure and vice versa |
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Normal boiling point |
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| Boiling point of a liquid when atmospheric pressure is 1.00 atmp or 760 torr is referred to as NORMAL BOILING POINT. | ||||
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