Aqueous sulfuric acid solutions containing 15.0 wt% H₂SO₄ and 80.0 wt% H₂SO₄ are mixed to form a 30.0 wt% product solution. The 15% solution was in a laboratory in which the temperature was 77°F. The 80% solution had just been taken from a storage cabinet in an air conditioned stockroom and was at a temperature of 60°F when the mixing occurred.

(a) The mass of the 15% solution is 2.30 lbm. What mass of 80% solution should be weighed out?

(b) Use Figure 8.5-1 to estimate the product solution temperature if the mixing is adiabatic.

(c) The product solution temperature eventually drops to (77°F). How much heat (Btu) is transferred from the solution to the laboratory air in this constant-pressure cooling process?

(d) The dilution can be carried out either by slowly adding the 15% solution to the 80% solution or vice versa. Use Figure 8.5-1 to determine the maximum temperature that would be attained using each procedure. Which procedure would be safer?

Figure 8.5-1

Transcribed Image Text:

140 120 100 80 60 40 20 -20 200°F -40 180 -60 -80 60 32°F 80 -100 40 -120 0.90 1.00 0.80 -140 0.70 0.50 0.60 0.40 0.30 0.10 0.20 Mass fraction of H,SO, A(Btu/lb, solution) Freezing line