Water in the bottom of a narrow metal tube $0\mathrm{.}5$ cm in

diameter is held at a constant temperature of $293$K$.$

The total pressure of air is $1$ atm and the temperature

is $293$K$.$ Water evaporates and diffuses through the air

in the tube and the diffusion path $($z $2$ z $1)$ is $0\mathrm{.}1524$ m

long. Calculate the rate of evaporation at steady state

in kmol $/$s$.$ The diffusivity of water at $293$K and $1$ atm is

$0\mathrm{.}250$x$104$ m $2/$s$.$ Assume that the system is

isothermal.