4. You want to purify 10 g of Compound A that has ben contamnted wih 0,2 g of Co

Question

4. You want to purify 10 g of Compound A that has ben contamnted wih 0,2 g of Compound B. Solubility in water of the two compounds are given in the following table. Compound Solubility at Compound A 0.029 Compound B 0.22 Solubility at 20° C (g/10 mL) 100°C (g10 mlL) 0.680 6.67 What volume of boiling water is needed to dissolve the 10 g of Compound A? (Show your calculation) a. How much Compound A will crystallize after cooling to 20°C? (Show your calculation) b. c. Will any Compound B crystals also form?

Explanation / Answer

(a)

In boiling water, 0.68 g of compound A dissolves in 10 mL volume.

So, 10 g of compound A will dissolve in: (10/0.68)*10 = 147 mL boiling water

(b)

At 200C, 10 mL water can only dissolve 0.029 g of compound A.

So,

147 mL of water will dissolve: (0.029/10)*147 = 0.426 g

So,

Mass of compound A that crystallizes = 10-0.426 = 9.574 g

(c)

At 200C, 10 mL water can only dissolve 0.22 g of compound B.

So,

147 mL of water will dissolve: (0.22/10)*147 = 3.23 g

Since compound B is present in less than this threshold limit, so no crystals of compound B will form.

Hope this helps !

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