You have a mixture containing 5.0 g of Compound X contaminated with 0.4 g of Com

Question

You have a mixture containing 5.0 g of Compound X contaminated with 0.4 g of Compound Y (total 5.4 g). Some data for the two compounds is given in the table below. A) What minimum volume of boiling water is needed to fully dissolve the 5.0 g of Compound X (assume all of the contaminant will dissolve as well in this same volume)? B) How much Compound X will crystallize out at 0 degree C? C) Will any of Compound Y crystallize out at 0 degree C? If so, how much? D) Will the crystals isolated from this recrystallization contain pure Compound X? E) The crystals obtained from the recrystallization above (parts A-C) are then re-dissolved in boiling water. What volume of boiling water will it take to dissolve the Compound X isolated in part B above? F) How much of Compound X will be obtained from this second recrystallization? G) Will any of Compound Y crystallize out at 0 degree C from this second recrystallization? If so, how much? H) Will the crystals isolated from this second recrystallization contain pure Compound X?

Explanation / Answer

A)

The minimum volume of boiling water that would be required to completely dissolve 5 g of compound X

Solubility of X in H2O at 1000C = 0.61/10ml

5g x 10mL/0.61g = 81.96 ml water

B) To determine how much Compound X will be soluble at 0°C in 81.96 mL of water. Set up a proportion:

0.03 g/10 mL = x g/81.96

X = 0.03g x 81.96ml/10ml = 0.25 g

So 5g – 0.25g = 4.75g

4.75g of compound X will crystallize out at 00C

C) To determine how much Compound Y will be soluble in 81.96 mL of at 0°C. Set up a proportion:

0.04 g/10mL = Y g/81.96 mL

Y = 0.04g x 81.96ml/10ml = 0.33 g

Yes compound Y will also crystallize out at 00C. Since mixture contains 0.4 g Compound Y, only 0.33g of Y is soluble.

So, 0.4g – 0.33g = 0.07g

0.07g of compound Y will crystallize out at 00C

D) No, the crystal isolated from this recrystallization does not contain pure X. There is 0.07g of compound Y also.

E)

The minimum volume of boiling water that would be required to completely dissolve 4.75 g of compound X

Solubility of X in H2O at 1000C = 0.61/10ml

4.75g x 10mL/0.61g = 77.87 ml water

F) To determine how much Compound X will be soluble at 0°C in 77.87 mL of water. Set up a proportion:

0.03 g/10 mL = x g/77.87

X = 0.03g x 77.87ml/10ml = 0.23 g

So 4.75 g – 0.23g = 4.52

4.52g of compound X will recrystallize out at 00C

G) To determine how much Compound Y will be soluble in 77.87 mL of at 0°C. Set up a proportion:

0.04 g/10mL = Y g/77.87 mL

Y = 0.04g x 77.87ml/10ml = 0.31 g

No, compound Y will not crystallize out at 00C , since mixture contains 0.07 g Compound Y

H) Yes, compound X is pure.

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