Unit X: Solutions & Solubility Curves 4 th Qtr – Spring 2011

1. Unit X: Solutions & Solubility Curves4th Qtr – Spring 2011 Mr. Gibson Chemistry Lecture Room 213 Laboratory Room 214

2. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solute:

3. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solute: The substance or “stuff” that gets dissolved (or diluted) in to some other medium.

4. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solvent:

5. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solvent: The medium or “stuff” that does the dissolving (of the solute).

6. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solution:

7. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Solution: What you have after you have dissolved your solute in a solvent.

8. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Soluble:

9. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Soluble: Any solute that CAN be dissolved in a solvent is said to be “soluble”.

10. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Insoluble:

11. Unit X: Solutions & Solubility Curves A quick review of some basic terms you have already learned: Insoluble: Any solute that canNOT be dissolved in a solvent; is said to be “insoluble” in that particular solvent. For eg. Lead sulfate is “water insoluble”.

12. Unit X: Solutions & Solubility Curves And now for some new terms or constructs. To give a more accurate description on a solute’s solubility… Three things have to be considered:

13. Unit X: Solutions & Solubility Curves And now for some new terms or constructs. To give a more accurate description on a solute’s solubility… Three things have to be considered: • The AMOUNT of solute.

14. Unit X: Solutions & Solubility Curves And now for some new terms or constructs. To give a more accurate description on a solute’s solubility… Three things have to be considered: • The AMOUNT of solvent.

15. Unit X: Solutions & Solubility Curves And now for some new terms or constructs. To give a more accurate description on a solute’s solubility… Three things have to be considered: • The temperature of the solution.

16. Unit X: Solutions & Solubility Curves And now for some new terms or constructs. A Solubility Curve is a plot of all three things but with one exception… The amount of the solvent is held constant at 100 mL. This means the amount of soluteand the temperature of the solution are both changed.

17. Unit X: Solutions & Solubility Curves The Solubility Curve

18. Unit X: Solutions & Solubility Curves The Solubility Curve The “Y” (vertical) axis of this plot is the number of grams of the solute that are dissolved in 100 mL (milliliters) of the solvent. On this graph the solvent is water.

19. Unit X: Solutions & Solubility Curves The Solubility Curve The “X” axis of this plots (horizontal) is the temperature of the solution between zero and one-hundred degrees Celsius.

20. Unit X: Solutions & Solubility Curves This plot or curve has several types of compounds that are “soluble” in water. As stated earlier, the plot shows how much of any given compound can be held in solution while the temperature changes.

21. Unit X: Solutions & Solubility Curves For example: Let’s look at sodium nitrate (NaNO3)

22. Unit X: Solutions & Solubility Curves For example: Sodium nitrate (NaNO3) has its curve plotted as a rising slightly curved line.

23. Unit X: Solutions & Solubility Curves For example: If we had a solution of the NaNO3 and its conditions were: 60 grams of this solute in 100 mL of water held at 30 degrees C…

24. Unit X: Solutions & Solubility Curves For example: The coordinates where these two conditions meet would be as indicated…

25. Unit X: Solutions & Solubility Curves For example: The data point of those two coordinates for Sodium nitrate (as indicated by the red circle) is BELOW the curve line… … and is therefore designated as being unsaturated.

26. Unit X: Solutions & Solubility Curves For example: And when we say it is unsaturated that term means the solution can take additional grams of solute and still keep them in solution.

27. Unit X: Solutions & Solubility Curves For example: And when we say it is unsaturated that term means the solution can take additional grams of solute and still keep them in solution.

28. Unit X: Solutions & Solubility Curves For example: Had the conditions been 80 grams of the solute NaNO3 held at 10 degrees Celsius… The data point would be ON the curved line and therefore would be considered to be saturated.

29. Unit X: Solutions & Solubility Curves For example: And by saturated we mean the solution canNOT take anymore of the solute NaNO3 and still remainin solution. This is the most that the solution can hold under those conditions.

30. Unit X: Solutions & Solubility Curves For example: And by super satured we mean the solution is being supplied with extra energy (usually in the form of mechanical mixing or some other means not yet discussed plus heat energy) [to] keep the extra solute in solution.

31. Unit X: Solutions & Solubility Curves The table also can tell us what we can predict will happen when conditions change –or- what we can then do should conditions change.

32. Unit X: Solutions & Solubility Curves For example: If we started with the following conditions for NaNO3: 110 grams held at 80 degrees C…

33. Unit X: Solutions & Solubility Curves 110 grams of NaNO3 held at 80 degrees C… would be an unsaturated solution because that coordinate lies BELOW the curve line.

34. Unit X: Solutions & Solubility Curves And since; The data point lies below the line – we can therefore calculate & predict how much moresolute the solution can hold under that set of conditions.

35. Unit X: Solutions & Solubility Curves Again, under this set of conditions the solution can take approximately an additional 40 grams of the solute NaNO3 150 – 110 = 40 grams

36. Unit X: Solutions & Solubility Curves Another way this chart can be used [is] as follows… Let’s say we have an unsaturated solution of NaNO3 held under the conditions of 110 grams @ 80 degrees C.

37. Unit X: Solutions & Solubility Curves And then you cool the solution down to 10 degrees C and no longer are stirring it…

38. Unit X: Solutions & Solubility Curves The new conditions would create a new coordinate of 110 g & 10 degrees C –or- as indicated by the purple colored circle.

39. Unit X: Solutions & Solubility Curves The new conditions indicate the solution went from an unsaturated solution under the old conditions (110 g @ 80 deg. C) [to] a supersaturated solution under the new conditions (the data point now lies ABOVE the curve).

40. Unit X: Solutions & Solubility Curves And since the new data point lies ABOVE the curve meaning it is a supersaturated solution… … the solution will precipitate out the difference (to the saturated –or- curve… see yellow line).

41. Unit X: Solutions & Solubility Curves And the amount of precipitate that will fall out of solution would be 110 g – 78 g (estimated) = 32 grams of precipitate.