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.

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.

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.

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.

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

To purify the solid substance P from impurity G, you can take advantage of the difference in solubility between P and G. Here are the steps you can follow:

1. Dissolve the sample in the minimum amount of water required to dissolve P completely at 25 degrees Celsius. Since the solubility of P is 1g/100 mL, you will need to use approximately 100 mL of water to dissolve the 10 g sample.

2. Heat the solution to 100 degrees Celsius. This will increase the solubility of both P and G.

3. Filter the hot solution to remove any insoluble impurities, if present. This step will help remove any solid impurities that did not dissolve in the hot solution.

4. Allow the hot solution to cool down slowly to room temperature or slightly below. As the temperature decreases, the solubility of P will decrease, but the solubility of G will remain the same.

5. As the solution cools, the solubility of P will decrease to its saturation point. This will cause some of the P to precipitate out of the solution in its pure crystalline form.

6. Carefully decant or filter the solution to separate the solid P crystals from the remaining liquid. This step will separate the purified P from the remaining solution and any residual impurities.

7. Wash the solid P crystals with a small amount of ice-cold water to remove any residual impurities that may have adhered to the crystals.

8. Finally, dry the purified P crystals to remove any remaining moisture. This can be done by allowing the crystals to air-dry or by using a drying oven.

By following these steps, you can isolate and purify the solid substance P from the impurity G, utilizing their difference in solubility.