Material Balances on Transient Processes: Example Problems

Try to solve these problems before watching the solutions in the screencasts.

Example Problem 1

Water is added to an empty 1100-L tank at a rate of 85 L/min. After 10 min, a valve opens and water flows out at a rate of 0.20V L/min. That is, the flow out is proportional to the height of water in the tank (and thus to the volume of water). Plot the volume of water in the tank as a function of time.

Example Problem 2

A tank contains 850 kg of a 5.0 wt% solution of sugar dissolved in water at 25°C. How long will it take to obtain a 15 wt% sugar solution if a 45 wt% sugar solution at 25°C flows into the tank at a flow rate of 20. kg/min? The tank is well mixed and at constant temperature.