Question

1 Kg of water (CP = 0.5 J/Kg^oC) is pumped to a height of 0.5 m, work done by the motor is 40 J/Kg, and heat liberated by it is 10 J/Kg, what is the final temperature of water if the initial temperature was 10^oC?

(a) 10^oC

(b) 30^oC

(c) 40^oC

(d) 60^oC

This question was posed to me in examination.

This question is from Application of the Energy Balance to Open Systems in chapter Application of Energy Balances in the Absence of Chemical Reactions and Energy Balances: How to Account for Chemical Reaction of Basic Chemical Engineering

Answer 1

Correct choice is (d) 60^oC

The explanation: ∆U = Q + W – m (∆H + ∆PE + ∆KE), => 0 = – 10 + 40 – 1*(∆H + 10*0.4), => ∆H = 25 J/Kg, => 25 = 0.5(T – 10), => T = 60^oC.