Question

A solid substance P is soluble in water (1g/100 mL) at 25 degrees and 10g/100mL of water at 100 degrees. You are given a sample that contains 10 g of P and 2g of impurity G. If G has the same solubility as P, describe how you could purify P.

Answer 1

Calculate the amount of water necessary to dissolve the 10g P (which will also dissolve all of the impurity G) at 100 C. Then calculate the amount of P and G that crystallizes at 25 C. You will get most of P back and about half of G. Then go through a second re-crystallization and see how much of P and G are left. If necessary you can go through a third and/or fourth.
The first is to use 100 mL H2O at 100 C which dissolves all of P and all of G. How much dissolves at 25 C? That will be
1g P x 100/100 = 1 g P dissolves so you must be left with 9 g P.
1g G x 100/100 = 1g G dissolves so you must be left with 1 g G. Now the mixture is 9g P + 1g G and you have reduced the impurity from about 17% to 10%. Now go through a second and/or third and/or a fourth as needed. Note that it will not take 100 mL water at 100 to dissolve 9g P + 1g G.

Answer 2

A solid substance P is soluble in water (1g/ 100mL) at 25°C and 10g/ 100mL of water at 100°C. You are given a sample that contains 10g of P and 2g of impurity G. Describe the procedure to purify P if G is insoluble in water.

Answer 3

You've just re-posted the same question. The answer to this one and the earlier post is the same. If you don't understand something I can explain if you care to tell me what's troubling you; however, I'm not going to work the entire problem for you. I worked the first part of it in detail and told you how to do the rest of the problem.

Answer 4

sorry, i actually posted it by accident. thank you for your help