Question

50 Kg of a solid liquid mixture containing 20% solid and 80% water is left open in the atmosphere, after some time the water is 60%, how much water is evaporated?

(a) 15 Kg

(b) 25 Kg

(c) 35 Kg

(d) 45 Kg

The question was asked during an interview for a job.

Question is taken from Solving Material Balance Problems for Single Units in portion A General Strategy for Solving Material Balance Problems and Solving Material Balance Problems for Single Units of Basic Chemical Engineering

Answer 1

Right option is (b) 25 Kg

To elaborate: Let the weight of the water evaporated be W. Water Balance: 0.8(50) = 1(W) + 0.6(50 – W), => W = 25 Kg.