Gas containing $0.8\: \mathrm{~mol} \%$ component $\text{A}$ is to be scrubbed with pure water in a packed bed column to reduce the concentration of $\text{A}$ to $0.1 \: \mathrm{~mol} \%$ in the exit gas. The inlet gas and water flow rates are $0.1 \mathrm{kmol} / \mathrm{s}$ and $3.0 \mathrm{kmol} / \mathrm{s}$, respectively.
For the dilute system, both the operating and equilibrium curves are considered linear. If the slope of the equilibrium line is $2$4 , the number of transfer units, based on the gas side, $N_{O G}$ is $\_\_\_\_\_\_$ (rounded off to $1$ decimal place).
