Question

HW #3 for Chem 318 Due: April 29, 2019 1. Solute A has a K 2.5 for an extraction between water (phase 1) and chloroform (phase 2). If 100 mL of a 0.01 fraction will be extracted? For the same solute and, what fraction will be extracted if 5 extractions wi 80 mL chloroform each are used (instead of one 400 ml extraction)? M solution containing solute A in water is extracted one time with 400 mL chloroform, what he retention volume of a solute is 85.5 ml for a column with Vm 18.2 mL and Vs 13.8 mL. Calculate the capacity factor and the partition coefficient for this solute 3. A solute is separated on a column (length: 25 cm) with a peak at 25.5 minutes (retention time) and the baseline width of the peak being o.7 minutes. Calculate the number of theoretical plates and the theoretical plate height of this column. 4. Two compounds (compound 1 and compound 2) are separated on a column with retention time being 14.6 minutes and 16.8 minutes, respectively. The baseline width of the two peaks is 0.8 minutes and 1.0 minutes, respectively. Are these two compounds separated completely? Why or why not? 5. Describe at some length the factors that contribute to the chromatographic peak broadening (hint: Why bands spread?) 6. List the types of liquid chromatography (categorized based on separation principles) and describe briefly the principles used for separation for each type. 7. What do the desirable properties for the immobilized liquid phase in a gas-liquid chromatographic column include? 8. What characteristics does an ideal detector for gas chromatography hav 9. Briefly describe the principle of operation for the following gas chromatographic detectors: 1).Flam lonization Detector (FID); 2).Thermal Conductivity Detector (TCD); 3).Electron-Capture Detector (ECD)
need help with number 2

Answer 1

Volume of stationary phase, Vs = 13.8 ml

Volume of mobile phase, Vm = 18.2 ml

Retention volume of solute, Vr = 85.5 ml

Partition coefficient/distribution coefficient, K = Cs/Cm = number of moles/ volume in stationary phase/number of moles/Volume in mobile phase = (retention volume of solute - volume of mobile phase)/volume of stationary phase =

= (Vr - Vm)/Vs = 85.5 ml - 18.2 ml/13.8 ml = 67.3/13.8 = 4.88

Capacity factor, k' =

K = k' (Vm/Vs) = 4.88

k' (18.2/13.8) = 4.88

k' = 67.344/18.2 = 3.7

Capacity factor, k' = 3.7