Chemical Process Calculations Lecture series - Lecture 46 Material Balance in Unsteady State systems and solved Numerical

In this lecture, The concept of material balance in an unsteady state system was explained. Overall material balance and individual material balance for a mixing tank as example was derived. Two numerical are solved in this lecture . Two practice problems are given in the end of this lecture. solve them and comment your answers. ----------- A tank contains 100 liters of a salt solution in which 5 kg of salt is dissolved. Water flows into the tank at the rate of 5 l/min and salt solution leaves the tank from the top at the same rate. Due to complete mixing, the concentration of salt in the tank is uniform all the times. Find the amount of salt remained in the tank at the end of 50 min. Take the density of the salt solution as 1 kg/l. ---- A tank contains 1000 kg of a 10% salt solution. A fresh stream containing salt at 20% salt solution enters the tank at 20 kg/min, and the mixture leaves the tank after complete mixing at a rate of 10 kg/min. i. Express the salt concentration as a function of time ii. At what instant of time, salt concentration will be 15% iii. What is the salt concentration after 2 hours. --- A tank contains 1000 kg of a 10% salt solution. A fresh stream containing salt at 20% salt solution enters the tank at 20 kg/min, and the mixture leaves the tank after complete mixing at a rate of 10 kg/min. i. Express the salt concentration as a function of time ii. At what instant of time, salt concentration will be 15% iii. What is the salt concentration after 2 hours--- -- A STORAGE tank contains 10000 KG a solution CONTAINING 5 % ACETIC ACID . A fresh feed of 500 kg per minute of pure water is entering the tank and dilutes the solution in the tank. The mixture is stirred well and the product leaves the tank at the rate of 500 kg per minute. At what instant of time, will the acid concentration in the tank drop to 1 % ? ---- Answers are subject to verification by the learners.