Two feeds, F1 with H = 10 J/mole and F2 with H = 25 J/mole, and product 15 moles with H = 15 J/mole, what is the F2?

Correct Answer: 5 mole
Energy balance: 10*F1 + 25*F2 = 15*15, => F1 + F2 = 15, => F2 = 5 mole.