Answer to Question #153694 in Physical Chemistry for Mani

Question

Liquid water and liquid sulfuric acid mix together to produce aqueous solution of sulfuric acid at 45C. Initially H2O(l) is at 25C temperature and 11kmol/h. H2SO4(l) is at 35C and 1.22kmol/h. Concentration of H2SO4(aq) is 35.7 wt%. Using concentration enthalpy chart, find the total heat needed to transferred during mixing operation.

Answer 1

M(H₂O) = 18 g/mol

M(H₂SO₄) = 98 g/mol

Concentration enthalpy chart:

$\Delta H_{mix}$ (45^oC, 35.7%) = -43 kcal/(kg solution) = -180 kJ/(kg solution)

C_p(H₂O) = 4.19 kJ/(kg/K)

$\Delta H$(H₂O heating) = 4.19*(45-25) = 83.8 kJ/kg

C_p(H₂SO₄) = 1.34 kJ/(kg/K)

$\Delta H$(H₂SO₄ heating) = 1.34*(35-25) = 13.4 kJ/kg

Q - total heat needed to transferred (per 1 hour)

Q = -($\Delta H_{mix}$ + $\Delta H$(H₂O heating) + $\Delta H$(H₂SO₄ heating)) =

-((11*18+1.22*98)*(-180)+11*18*83.8+1.22*98*13.4) = 38966 kJ/hour