you want to purify 10g of a compound A that has been contaminated with 0.20g of

ID: 889820 • Letter: Y

Question

you want to purify 10g of a compound A that has been contaminated with 0.20g of compound B. solubilities in water of the two compounds are given.

compound A - solubility at 20°c= 0.029g/mol, solubility at 100°c= 0.680g/mol

compound B - solubility at 20°c = 0.22, solubility at 100°c = 6.67

a) what volume of boiling water is needed to dissolve 10g of compound A?

b) How much of compound A will remain after cooling to 20°c?

c) what is the maximum amount of compound A that can be recovered in the first crop of this recrystallization?

d) will any compound B crystals form ( will compound B be pure)? show work to explain answer.

From the given data,

a) At 100 C , 0.680g/mol of compound A dissolves

to dissolve 10 grams amount of water required = 10/0.68 = 14.7 mole

mass of water required = 14.7*18 = 264.6 grams

volume of water required = 264.6 ml (density of water = 1 g/ml)

b) at 20 c, 0.029g/mol of compound A dissolves.

that means 18 grams of water contains 0.029 grams A

so that 18 ml of water contains 0.029 grams A.

therefore, 264.6 ml of water contains = 264.6*0.029/18

amount of compound A will remain after cooling to 20°c = 0.4263 grams

C) amount of compound A can be recovered = 10-0.4263

=9.5737 grams
d) compound B crystal can not be formed.because solubilty of B at 20 c

is 0.22 g/mol.but contaminated amount is only 0.2 grams.so no crystals are formed.

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