Question

Separating a Mixture, Recrystallization, pre-lab assignment

EXPERIMENT 4 Pre-Lab Assignment Separating a Mixture, Recrystalliration Name Date 1. Complete the following flowchart which shows how to separate a mixture of sand, sodium chloride and acetanilide. Notice that after a separation process (a down arrow) the filtered solids are shown on the left and the filtrate (the liquid) is shown on the right. The terminal step should give a pure product. (? next to arrows indicate procedures: 7 below arrows are the product of a procedure.) Then, on a separate sheet of paper, type a 300 word summary, in your own words, that explains the rationale behind your flowchart: what gets separated at each step, and why water is a useful solvent for this re- crystallization Sand, salt, acetanilide Obtain mass to 0.001 Mix with hot water, then filter Filtered material Filtrate (liquid that passes through filter) Drycrystals Filtered material Drycrystals 2. What are the characteristics of a solvent that are useful for recrystallization?

could you also explain why you chose that substance for the empty spaces and question marks

Answer 1

1) Sand + Salt + Acetanilide Mix with hot water, then filter Residue (filtered material) Filtrate Dry crystals Salt + Acetanilide Mix with cold water, Sand then filter Filtrate Residue (filtered material) Dry crystals Acetanilide Salt + water evaporate the water Salt 2) Characteristics of a Recrystallization Solvent: a. Substance should not be soluble in the solvent at room temprature but it should not dissolve at solvent's boiling point. b. Impurities should be maximum soluble at room temprature. c. Insoluble impurities should not be soluble even at boiling point. d. Solvent should be inert. e. The solvent should be volatile. f. The solvent should be inexpensive and easily available.

3) Total amount of acetanilide in the sample = 5.231*0.262 = 1.370 g Solubility of acetanilide = 0.0054g/mL Total amount of cold water = 45mL Amount of acetanilide remaining in water = 0.0054*45 = 0.243 g This is the amount of acetanilide, which you can not recover. Hence maximum acetanilide that could be recovered = 1.370-0.243 = 1.127 g 4) a) i) Sugar and water ii) Sodium bicarbonate (cooking soda) and water b) i) Sand + water ii) Benzene + water c) i) gaseous CO2 and dry ice (solid CO2) ii) gaseous CHCl3 with liquid CHCI3