A given mass of a gas occupies 919.0 mL in a dry state at STP. The same mass when collected over water at 15°C and 750 mm pressure occupies on litre volume. Calculate the vapour pressure of water at 15°C.
If p is the vapour pressure of water at 15°C, then P2 = 750 – p From the gas equation P1V1T1=P2V2T2, we get 760×919273=(750−p)×1000288 or p = 13.3 mm ∴ Vapour pr. of water = 13.3 mm.
