From the following information on compounds A, B, and C, predict which solvent o

Question

From the following information on compounds A, B, and C, predict which solvent of the ones listed would be the best to use to crystallize pure A from a mixture of the three with the least contamination from compounds B and C. Explain why the solvent was picked. Assume that the solubility of A, B, and C increase uniformly at higher temperatures. Suppose you wanted to recrystallize a 10.0 g sample of acetanilide from water. Answer the following questions using the water solubility information given Temperature (degree C): 0 degree 80 degree 100 degree Solubility, g/100 mL water: 0.53 3.5 5.5 How much boiling water would be necessary to dissolve the 10.0 acetanilide? How much of the 10.0 g of acetanilide would be left behind in the filtrate if and filtration were carried out at 0 degree C? What would be the maximum expected % recovery of the acetanilide? % recovery = g obtained as crystals/g sample used for crystallization times 100

Explanation / Answer

Q4.

a)

for 10 g... at T = 100°C we need:

5.5 g --> 100 mL water

10g --> x mL

x mL = 10/5.5*100 = 181.8 mL of water required

b)

10 g acetanilide left fter crystallization:

181.8 mL of water --> x mass of salt

100 mL -> 0.53

so

x = 181.8/100*0.53 = 0.96354 g will remain in solution

we had 10 g at 100°C

so

change in mass (crystals) = 10-0.96354 = 9.03646 g will be crystallized

c)

%expected recovery for this process = mass recovered / total mas sin solution * 100% = 9.03646/10*100 = 90.3646 %

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