1. Solubility and Solubility Curves

2. What are Solutions Made Of?
A solution is a homogeneous mixture of 2 or more substances in a single phase.
The substance being dissolved (or is less concentrated) is the SOLUTE.
The substance doing the dissolving (or is more concentrated) is the SOLVENT.

3. “like dissolves like”
Two substances with similar intermolecular forces are likely to be soluble in each other.
non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
polar molecules are soluble in polar solvents
C2H5OH in H2O
ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)
12.2

4. The Cleansing Action of Soap
12.8

5. Not All Things Dissolve the Same…
When a solid dissolves into a liquid, the particles of solid break down into their individual parts and spread out throughout the liquid
BUT… we’ve got some different vocab words for the type of solid doing this
Ionic compounds will dissociate into their separate ions
Ex: Ca(OH)2 (s)  Ca2+(aq) + 2 OH-(aq)

6. Electrolytes in the Body
Electrolytes are ionic solutions that conduct electricity.
Ionic compounds that dissociate easily are called Strong Electrolytes
Ionic compounds that don’t dissociate at all are called Non-electrolytes
Carry messages to and from the brain as electrical signals.
Important to maintain cellular function.

7. Covalent Compounds
Covalent compounds will still dissolve, but each molecule stays completely together, just spread further apart
This is called dispersion
Sugar is an excellent example of this
C6H12O6 (s)  C6H12O6 (aq)

8. Acids – The in-between ones
Acids are a bit special because they are covalent compounds, but they break into ions when mixed with water.
So they get a special term… Ionization!
Ex: HCl (g)  H+ (aq) + Cl- (aq)

9. Solutions are not just solids dissolved in liquids!
Solute
Solvent
Example
solid
Metal alloys 14-K Gold
liquid
Kool-Aid (Sugar in H2O)
Wine or Vinegar Alcohol or Acid in H2O
gas
Carbonate Beverages (CO2 in H2O)
Air (O2 and other gases in N2)

10. The amount of solute that dissolves in a specific amount of solvent.
Solubility is
The amount of solute that dissolves in a specific amount of solvent.
Expressed as grams of solute in 100 grams ( or ml) of solvent water.
Grams of solute
100 g/ml water

11. Unsaturated Types of Solutions
Contain less than the maximum amount of solute.
Can dissolve more solute.
Dissolved solute

12. Saturated Types of Solutions
Contain the maximum amount of solute that can dissolve.
Have undissolved solute at the bottom of the container.

13. Supersaturated Types of Solutions
An unstable solution that contains an amount of solute greater than normal.
Will start out with no extra solute on bottom, but will eventually appear

14. Simply adding in more solute DOES NOT create a supersaturated solution!
First, raise the temperature up to cause more solute to dissolve.
Next, lower the temperature back to where it was. NOW it’s a supersaturated solution!

15. Learning Check At 40C, the solubility of KBr is 80 g/100 g H2O.
Identify the following solutions as either
1) Saturated, (2) Unsaturated, or (3) Supersaturated
A. 60 g KBr added to 100 g of water at 40C.
B g KBr added to 200 g of water at 40C.
C. 25 g KBr added to 50 g of water at 40C.

16. A. 2 Amount of 60 g KBr/100 g water is less than the solubility of 80 g KBr/100 g water.
B In 100 g of water, 100 g KBr exceeds the
solubility of 80 g KBr water at 40C.
C This is the same as 50 g KBr in 100 g of water, which is less than the solubility of 80 g KBr/100 g water at 40C.

17. Solubility Curve
Saturated
Supersaturated
Unsaturated

18. Any point on a line represents a Saturated Solution.
Solubility Curve
Any point on a line represents a Saturated Solution.
In a saturated solution, the solvent contains the maximum amount of solute.
Example
At 90oC, 40 g of NaCl(s) in 100g H2O(l) represent a saturated solution.

19. Any point below a line represents an Unsaturated Solution.
Solubility Curve
Any point below a line represents an Unsaturated Solution.
In an unsaturated solution, the solvent contains less than the maximum amount of solute.
Example
At 90oC, 30 g of NaCl(s) in 100g H2O(l) represent an unsaturated solution.
How much is required to saturate the solution?

20. Solubility Curve
Any point above a line represents a Supersaturated Solution.
In a supersaturated solution, the solvent contains more than the maximum amount of solute. A supersaturated solution is unstable and the excess amount can precipitate or crystallize.
Example
At 90oC, 50 g of NaCl(s) in 100g H2O(l).
How much will NaCl(s) will precipitate?

21. Solubility Curve
Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

22. Temperature and Solubility
Solid solubility and temperature
Some compounds (usually solids) increase solubility with increasing temperature
Some compounds (usually gases) decreases solubility with increasing temperature
12.4

23. Chemistry In Action: The Killer Lake
Lake Nyos – formed from a former volcano that deposited large quantities of CO2 at the bottom of the lake.
It is not sure of the exact cause, but at some instant, 1.6 million tons of CO2 was released from the bottom of the lake.
As the gas erupted and covered the land, all oxygen was displaced and over 1,700 individuals and over 3,500 livestock were killed due to asphyxiation.
Lake Nyos, West Africa

24. Solubility Curves These curves represent saturated solutions.
Using these graphs, you can determine how many grams will dissolve at specific temperatures.