1. Solutions

2. Terms to know Solution – homogeneous mixture of a solvent and solute
Solvent – substance does the dissolving
Solutes – substance that gets dissolved
Aqueous solution – solution with water as the solvent

4. Solubility
Maximum amount of substance that will dissolve in a certain amount of water at a given temperature
Solubility of ionic substances
Ionic substances breakup into individual ions
Conducts electricity in water

5. Water is polar
Oxygen end is slightly negative (due to bigger electronegativity value)
Hydrogen end is slightly positive (due to smaller electronegativity value)

6. Polar substances like ionic substances

7. Polar dissolves polar Ethanol
Ethanol is soluble in water because of the polar OH bond

8. Why is sugar soluble in water?

9. Substances insoluble with water
Nonpolar substances
No polar end for water to be attracted to and pull apart
Ex: oil

10. Like dissolves like Polar dissolves polar Nonpolar dissolves nonpolar
Does water dissolve polar or nonpolar? Why?
What is similar about table salt and sugar that makes then dissolve in water?

11. How much can dissolve? The solubility of a solute is limited.
Saturated solution – contains as much solute as will dissolve at that temperature
Unsaturated solution – has not reached the limit of solute that will dissolve
More can dissolve

12. Supersaturated solution – occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved
Contains more dissolved solid than a saturated solution at that temperature
Unstable – adding a crystal causes precipitation
All of extra solute that made it supersaturated will fall to the bottom

13. Solubility Curve
Used to determine how much solute will dissolve in 100 g of H2O at a given temperature
ALWAYS use 100 g of water (same as 100 mL)

16. Another way to describe solutions
Solutions are mixtures
So amount of solute dissolved can vary
concentrated – relatively large amount of solute
dilute – relatively small amount of solute

17. Which solution is more concentrated?
B has more solute → more concentrated

18. Which solution is more concentrated?
They are the same! X has 2 in 1 L
Y has 4 in 2 L (just doubled!)

19. Factors affecting the rate of dissolving
Surface area
Dissolving occurs at the surface of the solid
Exposes more surface to be attracted to solvent
Stirring
Removes newly dissolved particles from solid surface
Exposes the surface to fresh solvent
Temperature (for solids)
Solvent molecules move more rapidly
Increases rate of dissolving

20. Review Questions What does, “like dissolves like” mean in chemistry?
Why does water alone not dissolve a grease stain?
Can a dilute solution also be saturated? Explain

21. Gases Solubility As temperature increases Particles move faster
Have energy to escape from a liquid
So solubility DECREASES when temperature goes up

22. Describing solution composition
Mass percent
Practice problem

23. Practice Problems
A 135 g sample of seawater is evaporated leaving 4.73 g of solid residue. What was the mass percent of solute present in the original seawater?
What mass of water must be added to 425 g of formaldehyde to prepare a 40.0% by mass solution?

24. Parts per million

25. Another way to describe solutions...

26. Finding number of moles
Moles will allow us to convert to grams (which is what can be weighed on a balance)

27. Practice Problems
Calculate the molarity of a solution that has 1 g of ethanol C2H5OH in 101mL 
How many grams of formaldehyde (HCHO) must be used to prepare 2.5 L of 12.3 M solution?

28. How to make a solution
Weigh out grams of solid (found from calculations)
Dissolve in most of the water
Fill to line with water once all is dissolved

29. Diluting a stock solution
Stock solution – concentrated
Dilute to make concentration that is needed
Moles of solute will remain the same (just adding more solvent)
M1 x V1 = M2 x V2
Molarity times volume before dilution = molarity times volume after dilution

30. Electrolytes
Substance that dissolves in water and produces ions that conduct electricity
Ex: NaCl
Nonelectrolyte – dissolves in water but does not allow the flow of electricity
Ex: sucrose

31. Colligative Properties
Any physical effect of the solute on the solvent
Solvent has its own set properties which are now changed due to dissolving something (solute) in it
So water no longer melts at 0 °C or boils at 100 °C because there is something mixed with it that hinders its ability to do that

32. What properties can change?
How well water mixes with other substances, freezing point, boiling point
Example – salt added to icy sidewalks
Salt lowers the freezing point of the water, so ice is able to melt at a lower temperature
Example - glycol in radiator
Increases the boiling point of the water in the radiator, which prevents overheating
Also lowers the freezing point, which is good for the radiator

33. Solute’s contribution to the property changes
Any solute (electrolyte or nonelectrolyte) contributes
How much dissolves and the concentration of the dissolved particles decides how much it changes the properties of the solvent
More dissolved particles  Greater concentration of those particles  bigger effect on boiling and freezing point

34. Dissolved particles
NaCl (s)  Na+1 (aq) + Cl-1 (aq) [2 dissolved particles]
C12H22O11 (s)  C12H22O11 (aq) [1 dissolved particle]
CaCl2 (s)  Ca+2 (aq) + 2 Cl-1 (aq) [3 dissolved particles]
So CaCl2 will have the biggest effect on colligative properties because it produces the most dissolved particles