A cylinder contains ethanol and is exposed to air in the room at $25C$ and $1$atm. the height of the cylinder is $30cm,$ diameter is $5cm.$ the height of ethanol in the cylinder is $7cm.$ Determine the time required to evaporate $50\%$ of mass of ethanol if the diffusion coefficient is $0\mathrm{.}023c\frac{m^2}{s}.$ The density of ethanol is $0\mathrm{.}789\frac{g}{c}{m}^3.$ The molecular weight of ethanol is $46\frac{g}{m}ol$ and the total flux is $2\mathrm{.}51{10}^{-4}mo\frac{l}{c}{m}^{2}s.$ "Hint not given just for you now: diffusion of $A$ in stagnant $B"$