Two feeds, F1 with H = 10 J/mole and F2 with H = 20 J/mole, and product 10 moles with H = 15 J/mole, what is the F1?

Correct Answer: 5 mole
Energy balance: 10*F1 + 20*F2 = 10*15, => F1 + F2 = 10, => F1 = 5 mole.