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3600_Ch23_probs - 23-1 23-7 23-8 23-21 23-27 33-40 23-43...

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Unformatted text preview: 23-1. 23-7. 23-8. 23-21. 23-27. 33-40. 23-43. Three extractions with 100 mL are more effective than one extraction with 300 mL. (21) SHgo # SCHCl3 K = [S]CHCl3/[S]H20 = 4-0 [S]CHC13 = K[S]H20 = (4.0)(0020 M) = 0.080M b molS in CHC13 _ (0.080 M)(10.0 mL) _ 050 ( ) mol 3 in H20 ‘ (0.020 M)(80.0 mL) ‘ - . . . __ V1 _ 80.0 6 _ Fraction remarnlng — (#VHKVZY — (#80.0+(4.0)(10.0)) — 0.088 9.0 — 3.0 (a) k :T = 2.0 (b) Fraction of time solute is in mobile phase = t7? = 3—9 = 0.33 _ - h _ A _ (c) K — k Vs — (2.0) 0.10 Vm — 20. (a) Column 1 (sharper peaks) (b) Column 2 (large plate height means fewer plates means broader peaks) (c) Column 1 (less overlap between peaks because they are sharper) (d) Neither (relative retention (= tr(B)/Tr(A)) is equal for the two columns (e) Compound B (longer retention time) (f) Compound B (longer retention time means greater affinity for stationary phase) Since w = 4Vr/W, w is proportional to Vr. w2/w1 = V2/V1 = 127/49 2? W2 = (127/49)(4.0) = 10.4 mL. _ .t'r_2 = 1‘2 (X _ t'rl ki 5.00 5.00 + 4.76 (a) Ifoc = 1.05 and ki = 5.00, ki =T05 = 4.76 and kév = ———2——- = 4.88. . W 1.05 — l 5.00 Resolution: 1.00 = 4 ( 1'05 )(1 + 4.88) 22> N=9.8>< 103 plates (b) 2.6 x 103 plates (c) 8.2 x 103 plates ((1) N can be increased by increasing the column length (N oc xii). 0t can be increased by changing solvent and/or stationary phase to change the partition coefficients of the two components. kz' can be increased by increasing the volume of stationary phase. In this problem 0t has a much larger effect than kz'. ...
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