Consider Problem 14.41.
(a) How long should the bubbles remain in the water to achieve an average vapor concentration that is 95% of the maximum value?
(b) How long should the bubbles remain in the water to achieve an average vapor concentration that is 50% of the maximum value?

Data From Problem 14.41

A common procedure for increasing the moisture  content of air is to bubble it through a column of  water. Assume the air bubbles to be spheres of radius  r_o = 1 mm and to be in thermal equilibrium with the  water at 25°C. How long should the bubbles remain in  the water to achieve a vapor concentration at the center  that is 99% of the maximum possible (saturated)  concentration? The air is dry when it enters the water.