Some discarded solid chemical waste dissolves slowly in a large drain pipe in which the water is stagnant. On a particular day, the dissolved chemical has a concentration of 0.16 M near the solid and is essentially 0 at a location 13.6 m further along the pipe. The transfer rate (moles per time) of the chemical through the water in the pipe between those two points is 7.3 gmol/min.
a. What equation describes this kind of transfer?
b. Several days later, the chemical concentration near the solid has decreased to 0.105 M and is essentially 0 at a location 9.9 m away. What will be the transfer rate between the point near the solid and the point 9.9 m away on this later day?
c. On the next day, the heavy rains cause a current of water to flow through the drain pipe where the dissolving solid is located. The solid now dissolves twice as fast as on the previous day. If the concentrations are still 0.105 M near the solid and 0 at the more remote locations, and if the cross-sectional area for transfer is 0.3 m², what is the value of the mass-transfer coefficient at this time?