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Calculate the weight of water in grams per litre of air at 20^(@)C and 45% relative humidity. Vapour pressure of water at 20^(@)C is 17.5 mmHg. |
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Answer» Solution :We have that, % relative humidity `= ("partial pressure of " H_(2)O "in air")/("vapour pressure of " H_(2)O " at the same temp.") XX 100` `therefore p_(H_(2)O) = (45 xx 17.5)/(100) = 7.9 m m= 0.0104` atm. Thus for 1 litre of air, MOLE of `H_(2)O` can be calculated as, `n = (pV)/(RT) = (0.0104 xx 1)/(0.0821 xx 293) = 4.3 xx 10^(-4)` mole. `therefore` WT. of `H_(2)O = 4.3 xx 10^(-4) xx 18 = 7.74 xx 10^(-3)` g/L of air. |
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