Separation Process Principles- 2n - Seader &amp; Henley - Solutions Manual

# 9 15 10 10 b cp 057 117 060 032 dab w c 189 x

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: B 7.4 × 10 −8 φ B M B = 0 µ Bυ A.6 1/ 2 T (1) From Table 3.3, υA = 14.8 + 4(21.6) =101.2 cm3/mol Using Eq. (1) with the following parameters, values of diffusivity are computed. Solvent, B Methanol Ethanol Benzene n-Hexane MB 32 46 78 86 φΒ 1.9 1.5 1.0 1.0 µB , cP 0.57 1.17 0.60 0.32 DA,B (W-C) 1.89 x 10-5 0.98 x 10-5 2.03 x 10-5 4.00 x 10-5 DA,B (Expt.) 1.69 x 10-5 1.50 x 10-5 1.92 x 10-5 3.70 x 10-5 Except for ethanol, the Wilke-Chang equation makes good predictions. The applicable Hayduk-Minhas equation, Eq. (3-42), is, DA,B = 155 × 10 −8 . T 1.29 PB0.5 / PA0.42 (2) µ 0.92υ 0.23 B B where, for the nonpolar solute, CCl4 , with methanol and ethanol solvents, both P B and υB must be multipled by 8µB in cP. Parachors for methanol and benzene are obtained from Table 3.5. Parachors for ethanol, n-Hexane, and carbon tetrachloride are obtained by structural contributions from Table 3.6. Using Eq. (2) with P A= 229.8 and the following parameters, values of diffusivity are computed. Solvent, B PB υB µB , cP DA,B (H-M) DA,B (Expt.) Methanol 88.8 37.0 0.57 2.55 x 10-5 1.69 x 10-5 Ethanol 125.3 59.2 1.17 1.70 x 10-5 1.50 x 10-5 -5 Benzene 205.3 96.0 0.60 1.96 x 10 1.92 x 10-5 n-Hexane 271.0 140.6 0.32 3.05 x 10-5 3.70 x 10-5 Except for methanol and n-hexane, the predictions by the Hayduk-Minhas equation are good. Exercise 3.12 Subject: Estimation of the diffusivity of benzene (A) at infinite dilution in formic acid (B) at 25oC and comparison to the experimental value for B at infinite dilution in A. Given: Experimental value of 2.28 x 10-5 cm2/s for the diffusivity of B at infinite dilution in A. Find: Diffusivity by the Hayduk-Minhas equation, (3-42). Analysis: The applicable H-M equation is, DA,B = 155 × 10 . −8 T 1.29 PB0.5 / PA0.42 µ 0.92υ 0.23 B B (1) From Table 3.5, parachors for A and B are 205.3 and 93.7, respectively. From Table 3.3, The molar volume of the solvent, B, is 2(3.7)+14.8+7.4+12.0 = 41.3 cm3/mol. From Perry's Handbook, the viscosity of B at 25oC is 1.7 cP. Using Eq. (1), DA,B = 1.55 × 10 −8 2981.29 ( 93.7 0.50 / 205.30.42 ) (1.7) 0.92 (41.3) 0.23 = 6.5 × 10−6 cm 2 /s This is significantly less than the experimental value of 2.28 x 10-5 and the predicted value of 2.15 x 10-5 cm2/s for the diffusivity of formic acid at infinite dilution in benzene. Exercise 3.13 Subject: Estimation of the liquid diffusivity of acetic acid at 25oC (298 K) in dilute solutions of benzene, acetone, ethyl acetate, and water, and comparison with experimental values. Given: Experimental values. Find: Infinite dilution diffusivities for acetic acid (A) in the four solvents using the appropriate equation. Analysis: For benzene, acetone, and ethyl acetate, Eq. (3-42) of Hayduk-Minhas applies: DA,B = 155 × 10 . −8 T 1.29 PB0.5 / PA0.42 (1) µ 0.92υ 0.23 B B From Table 3.5, the parachor for acetic acid = P A = 131.2. For all three solvents, this value is multiplied by 2 to give 262.4. Parachors for benzene and acetone are obtained from Ta...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online