1. If a mixture of two or more substances in solution is allowed to crystallize by decreasing the temperature of the solution, the crystals will contain more of the least soluble substance
CRYSTALLIZATION – A method of separating substances based on differences in solubility
EX7-1 (of 13)

2. EX7-2 (of 13)

3. 35 g A, 5 g B
100 g H2O at 100°C
Dissolved
Crystallized
EX7-3 (of 13)

4. 70 g A are soluble at 100ºC, so all 35 g A will dissolve
50 g B are soluble at 100ºC, so all 5 g B will dissolve
EX7-4 (of 13)

5. 35 g A, 5 g B
100 g H2O at 100°C
Dissolved
Crystallized
35 g A, 5 g B
nothing
100 g H2O at 0°C
Dissolved
Crystallized
EX7-5 (of 13)

6. 5 g A are soluble at 0ºC, so 5 g A will dissolve
 the rest of the A (35 g - 5 g) will crystallize out
10 g B are soluble at 0ºC, so all 5 g B will dissolve
EX7-6 (of 13)

7. 85.7% of A has crystallized out
35 g A, 5 g B
100 g H2O at 100°C
Dissolved
Crystallized
35 g A, 5 g B
nothing
100 g H2O at 0°C
Dissolved
Crystallized
5 g A, 5 g B
30 g A
85.7% of A has crystallized out
The crystals are 100% A
EX7-7 (of 13)

8. What if only half the water is used?
EX7-8 (of 13)

9. 35 g A, 5 g B
50 g H2O at 100°C
Dissolved
Crystallized
EX7-9 (of 13)

10. 35 g A are soluble at 100ºC, so all 35 g A will dissolve
25 g B are soluble at 100ºC, so all 5 g B will dissolve
EX7-10 (of 13)

11. 35 g A, 5 g B
50 g H2O at 100°C
Dissolved
Crystallized
35 g A, 5 g B
nothing
50 g H2O at 0°C
Dissolved
Crystallized
EX7-11 (of 13)

12. 2.5 g A are soluble at 0ºC, so 2.5 g A will dissolve
 the rest of the A (35 g – 2.5 g) will crystallize out
5 g B are soluble at 0ºC, so all 5 g B will dissolve
EX7-12 (of 13)

13. 92.9% of A has crystallized out
35 g A, 5 g B
50 g H2O at 100°C
Dissolved
Crystallized
35 g A, 5 g B
nothing
50 g H2O at 0°C
Dissolved
Crystallized
2.5 g A, 5 g B
32.5 g A
92.9% of A has crystallized out
The crystals are 100% A
EX7-13 (of 13)