An aqueous solution of sodium acetate (20.0 mol% NaC2H3O2) flows at a rate of 100 kg/h into an evaporative crystallizer at 60°C. When the solution is exposed to the low pressure in the evaporator 16.9% of the water evaporates, concentrating the remaining solution and causing crystals of sodium acetate trihydrate (NaC2H3O2.3H2O) to form. The product is an equilibrium mixture of crystals and a saturated aqueous solution containing 15.4 mol% NaC2H3O2. The effluents (crystals, solution, and water vapor) are all at 50°C.
Estimate the rate at which heat must be transferred to or from the crystallizer (state which), using the following physical property data:
Cp, all solutions = 3.5 kJ/(kg °C)
Cp, crystals = 1.2 kJ/(kg °C)
Cp, H2O(v) = 32.4 kJ/(kmol °C)
ΔÄ¤v,H2O = 4.39 x 104 kJ/kmol
Heat of solution of anhydrous sodium acetate: ΔÄ¤s(25 °C) = -1.71 x 104 kJ/kmol NaC2H3O2
Heat of Hydration: NaC2H3O2(s) + 3 H2O (l) à NaC2H3O2.3H2O (s) ΔÄ¤(25 °C) = -3.66 x 104 kJ/kmol NaC2H3O2
The question belongs to Chemistry and it discusses about calculating the rate at which heat must be transferred to or from the crystallizer. This has been discussed in the solution detail.
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