A pool of water 1 mm in depth lies on a horizontal surface in contact with dry air at 20°C and a pressure of 1 atm (101325 N m^-2). Evaporation takes place and can be treated as molecular diffusion through a 5 mm thick film of moist air immediately above the water\'s surface. Above this gas film, water vapour is assumed to be perfectly mixed with the surroundings ( the partial pressure of water vapour is zero). Assuming that evaporation does not affect the temperature of the water, calculate the molar flux of water vapour from the surface and the time taken for complete evaporation of the liquid. You will need to find the vapour pressure.

Diffusion coefficient for water vapour in air = 2.6x10^-5 m² s^-1