1. Reading Solubility Curves

2. What is Solubility?
Solubility: the maximum amount of solute that will dissolve in a certain amount of solvent at a given temperature
Solute = substance dissolved
Solvent = does the dissolving
Example: __ grams of salt (NaCl) in 100 g of water at __ ˚C.

3. Temperature and Solubility
Temperature affects how much of the solute can be dissolved by the solvent.
Note: Increasing the temperature does not always increase the solubility…think about what happens to dissolved gas in your soda when its heated
Solubility curves: used to show how the solubility of a substance changes with temperature.

4. To read the graph: 1. Find the line for the substance. 2
To read the graph: 1. Find the line for the substance. 2. The amount that dissolves at a given temp. is on the y-axis.

5. How much KNO3 dissolves in 100g H2O at 50oC?
Find the line (red)
Find the temperature and follow up to the line. (green)
Read across to the y-axis and this is the answer. (blue)
Since it is above the ½-way between 80 and 90, 87g KNO3 will dissolve.

6. Types of Solutions: Saturated solution: point on the line
Contains maximum amount of solute at given temp
Contains what it should hold
Supersaturated: above the line
Contains more solute than a saturated solution
Contains more than it should hold
Unsaturated: below the line is
Contains less solute than saturated solution
Contains less solute than it could hold

7. supersaturated
Saturated
Unsaturated

8. SOLUBILITY GRAPHS temperature KNO3 140 120 KBr 100 NaNO3 NH4Cl 80 60.
SOLUBILITY GRAPHS
KNO3
140
120
KBr
100
NaNO3
NH4Cl 80 60
Concentration (g/100 g water) 40
NaCl
Na2SO3 20 10 20 30 40 50 60 70 80
temperature

9. SOLUBILITY FORMULAS = amount of solute amount of solute
amount of solvent
amount of solute
amount of solvent =
Given solubility unknown

10. 1.The solubility of a solid is
SOLUBILITY PROBLEMS
1.The solubility of a solid is
15g / 100g of water. How many grams of the solid must be dissolved in 1 kg of water to make a saturated solution?

11. SOLUBILITY PROBLEMS 15 g ------- 100g X ------- 1000g X=150g
amount of solute
amount of solvent
amount of solute
amount of solvent =
15 g
100g X
1000g
X=150g =

12. SOLUBILITY EXAMPLES 15g ------ 100g X ------ 500g =
2. If you have 50g in 500g of water, using solubility from problem #1, is the solution saturated?
15g
------
100g X
------
500g
X=75g is saturated =
No, 50 g is not saturated!

13. SOLUBILITY EXAMPLES 5g X X=12.5g to prepare a saturated solution -----
3. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. How much of the solute must be dissolved in 250g of water at 20 C to prepare a saturated solution? 5g
-----
100g X
-----
250g
X=12.5g to prepare a saturated solution =

14. SOLUBILITY EXAMPLES
4. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. If a saturated solution is prepared using 200g water at 50 C, then allowed to cool to 20 C:
a. Will it still be saturated?
b. How much solute will precipitate out?

15. SOLUBILITY EXAMPLES 7.5g X
Will it still be 50 C:
7.5g
-----
100g X
-----
200g
X=15g to prepare a saturated 50 C =

16. SOLUBILITY EXAMPLES 5g X X=10g to prepare a saturated solution @ 20 C
Will it still be saturated? Now cool it to 20 C: 5g
-----
100g X
-----
200g
X=10g to prepare a saturated 20 C =

17. SOLUBILITY EXAMPLES 15g > 10g @ 20 C so its supersaturated!!
Will it still be saturated? Now cool it to 20 C:
15g
>
10g
@ 20 C so its supersaturated!!

18. SOLUBILITY EXAMPLES 5g ----- 100g X ----- 200g
How much will precipitate out? 5g
-----
100g X
-----
200g
X=10g to prepare a saturated 20 C =
7.5g
-----
100g
X=15g to prepare a saturated 50 C X
-----
200g =

19. SOLUBILITY EXAMPLES 15g - 10g = 5g will precipitate out!
How much will precipitate out?
15g - 10g = 5g will precipitate out!

20. To do Calculations: To calculate how much extra has been dissolved:
Extra = Dissolved amt saturated
in soln (given value) line that temp.
To calculate how much more can be dissolved:
? Much more = saturated given value
line that temp

21. Example 1:
How much less KCl is dissolved at 20oC than at 60oC in 100g H2O?
Read the line value:
32g at 20oC
Subtract it from the
given value:
45g – 32g = 13 g

22. Example 2:
How much more KCl is required to saturate the solution if 25g are dissolved at 40oC?
Read the line value:
40g
Subtract the given
value:
40g – 25g = 15 g

23. Your turn! Use your graph
How much NaCl will dissolve in 100g H2O at 35oC?
How much NH4Cl will dissolve at 50oC?
What is the solubility of SO2 at 25oC?
What is the solubility of potassium chlorate in 100 grams of water at 35oC?
What is the solubility of potassium iodide in 100 grams of water at 10oC?

24. What minimum temperature needed to dissolve 80 grams of sodium nitrate in 100 grams of water?
What minimum temperature needed to dissolve 42 grams of potassium chloride in 100 grams of water?
What minimum temperature needed to dissolve 20 grams of KClO3 in 100 grams of water?
If 95 grams of potassium nitrate are mixed with 100 grams of water at 45ºC, how much will not dissolve?
If 85 grams of potassium iodide are mixed with 100 grams of water at 0ºC, how much more must be added to saturate the solution?

25. If 55 grams of potassium chlorate are mixed with 100 grams of water at 55ºC, how much will not dissolve?
If 125 grams of potassium iodide are mixed with 100 grams of water at 10ºC, how much more must be added to saturate the solution?
What is the solubility of potassium chlorate in 50 grams of water at 35ºC?

26. What is the solubility of potassium chlorate in 100 grams of water at 35 oC?
What is the solubility of potassium iodide in 100 grams of water at 10 oC?
What is the minimum temperature needed to dissolve 80 grams of sodium nitrate in 100 grams of water?
What is the minimum temperature needed to dissolve 42 grams of potassium chloride in grams of water?
What is the minimum temperature needed to dissolve 20 grams of KClO3 in 100 grams of water?

27. If 95 grams of potassium nitrate are mixed with 100 grams of water at 45 oC, how much will not dissolve?
If 55 grams of potassium chlorate are mixed with 100 grams of water at 55 oC, how much will not dissolve?
If 125 grams of potassium iodide are mixed with 100 grams of water at 10 oC, how much more must be added to saturate the solution?
If 85 grams of potassium iodide are mixed with 100 grams of water at 0 oC, how much more must be added to saturate the solution?
What is the solubility of potassium chlorate in 50 grams of water at 35 oC?

28. Turn in your work

29. Gas Solubility
1C.12 & 1C.13

30. What About Gases?
We’ve seen that for most solids, the solubility usually increases as temperature __________
Does the same hold true for gases??
What does this graph tell us?
What type of relationship is shown between solubility and water temperature?
increases
Temp ↑
Solubility ↓
Inverse

31. Gas Solubility
As seen from the graph, as the water temperature __________ the gas solubility _________
Looking at the graph very closely…
Even at low temperatures, would you say that gases are VERY soluble?
increases
decreases
Most gases are far less soluble than many ionic solids

32. The Pressure’s ON!!
Because most gases do not dissolve very well, solutions are put under high pressures to increase the gas solubility.
For example…CO2 from a high-pressure tank must be forced into the soda container just before it is sealed
This high pressure is quickly decreased when the container is opened
The longer the beverage is open to the air, the more CO2 escapes (“flat”)

33. Factors Affecting Gas Solubility
What relationship is shown in the graph?
What type of relationship is this?
Based on what we’ve discussed, what factors would you say affect gas solubility?
Temperature
Nature of Solvent
Pressure
Pressure ↑
Solubility ↑
Direct
A linear graph with a positive slope = direct relationship

34. Affects on the Environment
Oxygen dissolved in water is necessary for aquatic wildlife to survive.
What if the temperature of the water increases?
The amount of dissolved oxygen _______
Also, as temperature increases, cold-blooded animals’ (fish) metabolism increases – they require more oxygen
What causes water temperatures to increase?
summer heat, power plant cooling water, etc.

35. Can There Be Too Much O2? YES!!!
When O2 dissolves, so does N2 (both in the air)
Gas Bubble Trauma: bubbles form in the blood and tissues of fish
O2 can be used during metabolism
N2 bubbles block capillaries resulting in the death of the fish

36. How Does it Happen?
Supersaturation (110% to 124%) of O2 and N2 happens at the base of dams
Released water forms “froth,” trapping large quantities of air