Question

A mass of 70 kg of 15-wt-% solution of H₂SO₄ in water at 70 ^oC is mixed at atmospheric pressure with 110 kg of 80-wt-% H₂SO₄ at 38^oC. During the process heat in the amount of 20,000 kJ is transferred from the system. Determine the temperature of the product solution

Answer 1

I have doubt in the term "process heat in the amount of 20,000 kJ is transferred from the system"

<<is it energy transferred out of the system or energy is absorbed by the system. I have considered both the case. 1st case is done with energy being transferred out of the system while the second case is considered with energy being absorbed by the system. >>

Let us assume the specific heat of H2so4 = Cp = 1.34 KJ/kg K and it is constant for varying composition and temperature.

Let Process heat of the solution = Heat of Mixing = E = 20,000 KJ

Let T1 = 70 deg C, W1 = 70 Kg

T2 = 38 Deg C W2, = 110 Kg

1st case with energy being transferred out

Let T be the final temperature achieved without the heat of solution is considered.

T = (w1 * T1 / W) + (w2 * T2 / W)

T = 50.44 deg C

2nd case with energy being absobed by the system.

Let T3 be the final temperature achieved with the heat of solution is considered.

T3 = T + (E/W * Cp)

T3 = 50.44 + (20,000/180 * 1.34)

T3 = 133.44 deg C