Estimate the average mass$-$transfer coefficient of absorption of $C{O}_2$ into water film flowing down a vertical wall $1m$ long at the rate of $0\mathrm{.}02k\frac{g}{s}$ per metre of water width at $25C.$ The gas is pure $C{O}_2$ at $1std$ atm. The water is essentially $C{O}_2-$free initially.

The solution density is $0\mathrm{.}998\frac{g}{c}{m}^3.$