# ps 3 solution - Chemistry420 Problemset#3(80pointstotal)Key

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Chemistry 420 Problem set #3 (80 points total) —Key Due at the beginning of class October 29 No late assignments will be accepted. Assignments are due at beginning of class—starts at 12 Noon! For full credit assignments must be in box when the lecture begins. Any assignment turned in between noon and 12:05 PM will automatically be deducted 5 points. Assignments will NOT be accepted for credit after 12:05 PM. Score = 0 No name, no grade. Show all of your work for each answer. Partial credit will be given and NO credit will be awarded if no work is shown. Be careful to use correct significant figures. 1. (12 points, Skoog 26 14) The following data are for a liquid chromatographic column Length of packing 24.7 cm Flow rate 0.313 mL/min V M 1.37 mL V S 0.164 mL A chromatogram of a mixture of species A, B, C, and D provided the following data: Retention time, minutes Width of Peak Base ( W ), minutes Nonretained 3.1 A 5.4 0.41 B 13.3 1.07 C 14.1 1.16 D 21.6 1.72 Calculate: a) the number of plates from each peak. b) the mean and the standard deviation for N. c) the plate height for the column. (a) 2 points for setup, 1 point for each answer, 0.5 for sig figs 2 2 2 3 3 2 3 16 5.4 13.3 for A: 16 2775 or 2.8x10 or 2800 plates for B: 16 2472 or 2.47x10 or 2470 plates 0.41 1.07 14.1 for C: 16 2365 or 2.36x10 or 2360 plates fo 1.16 R t N W N N N = = = = = = = 2 3 21.6 r D: 16 2523 or 2.52x10 or 2520 plates 1.72 N = = (b) 1 point for each setup, 1 point for each answer, 0.5 for sig figs ( ) ( ) ( ) ( ) 3 2 2 2 2 2 2775 2472 2365 2523 2534 or 2.53x10 plates 4 2775- 2534 2472- 2534 2365- 2534 2523- 2534 174 or 2x10 4-1 N SD + + + = = + + + = =

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