Problem $1.$

Determine the mass$-$transfer coefficient and the flux for mass transfer $($in kmo$\frac{l}{m^2}s)$ from a

$30mm$ in diameter solid sphere of a volatile substance to a gas at $60C$ and $2\mathrm{.}5$atm flowing

at an average velocity of $0\mathrm{.}5\frac{m}{s}.$ The diffusivity of the substance in the gas at $1$atm and

$40C$ is $2*{10}^{-6}\frac{m^2}{s}$ and the vapour pressure of solid substance is $8mm{H}_{2}O.$ Density of the

gas at $60C$ and $2\mathrm{.}5$atm is $1\mathrm{.}2k\frac{g}{m^3}$ and viscosity $2*{10}^{-5}Pa*s.$