Question

A brine solution of salt flows at a constant rate of 77 ​L/min into a large tank that initially held 100100 L of brine solution in which was dissolved 0.150.15 kg of salt. The solution inside the tank is kept well stirred and flows out of the tank at the same rate. If the concentration of salt in the brine entering the tank is 0.030.03 ​kg/L, determine the mass of salt in the tank after t min. When will the concentration of salt in the tank reach 0.010.01 ​kg/L?

Answer 1

Explanation: i) Mass per capacity of the tant = (0.15015/100100) kg/L = 0.0000015 kg/L

Amount salt of concentrated salt left = ( 0.03003 - 0.0000015) kg/L = 0.0300285 kg/L

∴ mass of salt in the tank = 0.0300285 kg/L X 77 L/min = 2.31 kg

ii) Capacity of tank at 0.01001 kg/L: 2.31 kg/0.01001 kg/L = 230.77 L

∴ time taken for the concentration of the salt = 230.77/(77 L/min) = 3 minutes.