1. A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute depends on temperature, pressure, and whether the solute and solvent are polar or nonpolar. 2. Solubility curves show the maximum amount of solute that can dissolve at different temperatures. Lines that increase with temperature represent solid solutes, while lines that decrease represent gas solutes. 3. Concentrated solutions have a higher number of moles of solute per liter of solution (molarity) than dilute solutions. Adding salts to water lowers its freezing point and raises its boiling point.

1. Solutions and Solubility

2. Solutions
• Solution – a homogenous mixture of a
solute dissolved in a solvent. The
solubility (ability to dissolve) of a solute in
a solvent is dependent on the
1. Temperature
For solid solutes: as temperature
increases, solubility increases.
For gas solutes: as temperature
increases, solubility decreases.

3. Solutions con
2. Pressure
For solid solutes: as pressure increases,
solubility remains the same.
For gas solutes: as pressure increases,
solubility increases
3. Nature of Solute/Solvent
“Like dissolves in like.”

4. Solute/Solvents cont.
Solubility Summary
Solute Type Nonpolar
solvent
Polar Solvent
Nonpolar (Fat
Grease)
Soluble (soap) Insoluble
(water)
Polar Insoluble Soluble (water)
Ionic (salt) insoluble Soluble (water)
High solubility-soluble Low solubility-insoluble

5. Solubility Curves
• Shows the number of grams of solute that can be
dissolved in 100.g of water at temperatures between 0
degrees C and 100 degrees C.
• Each line represents the maximum amount of that
substance that can be dissolved at a given temperature.
• Lines that show an increase in solubility as temperatures
increase represent solids being dissolved in water.
• Lines that show a decrease in solubility as temperatures
increase represent gases being dissolved in water.
These are NH3, SO2, and HCl

6. There are three types of solutions
• 1. An unsaturated solution is a solution in which
more solute can be dissolved at a given
temperature.
• 2. a saturated solution is a solution containing
the maximum amount of solute that will dissolve
at a given temperature.
• 3. a supersaturated solution is a solution that
contains more solute than would dissolve in a
saturated solution at a given temperature.

7. Solubility Rules
• Not all ionic compounds are water soluble
• There are some general rules for
compounds that are water soluble:
– Group 1 ionic cmpds and ammonium (NH4
+)
are always water soluble
– Group 17 ionic cmpds are water soluble
except when paired with Ag, Pb, and Hg ions
– See Table F for full rules and exceptions

8. Examples
• AgNO3 = water soluble
• AgCl = insoluble
• Na2S = soluble
• NaCl = soluble
• CaCO3 = insoluble
• AlPO4 = insoluble

9. Precipitation reactions
• Recall that double-replacement reactions
have the general formula:
AB(aq) + CD(aq) AD(aq) +CB(s)
A precipitation reaction will take place if one
or both of the products is listed as an
insoluble solid.

10. 2KI(aq) + Pb(NO3)2(aq) -> 2KNO3(aq) + PbI(s)
• KI = soluble
• Pb(NO3)2 = soluble
• 2KNO3(aq) = soluble
• PbI(s) = insoluble solid
• In a precipitation reaction, two clear
aqueous solutions are combined to form a
cloudy, solid precipitate that can be
collected by filtration.

11. Concentrations of Solutions
• Because solutions are homogeneous
mixtures, their compositions can vary.
Sometimes it is adequate to refer to a
solution as dilute or concentrated. These
are qualitative descriptions of
concentration. It is more precise to
describe the concentration of solutions in
quantitative measures.

12. Molarity
• Molarity (M)- number of moles of solute in 1L of
solution. Table T
Molarity= moles of solute
liters of solution

13. Calculating molarity
Highly concentrated HCl(aq) has a molarity
of 12M
This means there are 12 moles of HCl
dissolved in 1 Liter of water
12M = 12 moles
1 Liter

14. Sample Problem
• How many grams of NaCl must be added
to 1 Liter of water to make a 3M solution?
• 3M = 3 moles NaCl
I Liter
1 mole NaCl = 58g x 3moles = 174g NaCl

15. Parts Per Million
• Parts per million is another way of
measuring the concentration of a solution
• The general formula is:
Parts per million = grams of solute x 1,000,000
grams of solution

16. Parts per million example
• 5 grams of NaCl is dissolved in 2.5L of
water. What is the concentration of NaCl
in parts per million (ppm)?
• Remember 1mL water = 1 g
ppm = 5g NaCl x 1,000,000 = 2000 ppm
2500 g H2O

17. Colligative Properties
Freezing and boiling points of water change when salts
(nonvolatile solutes) are added. Colligative properties
depend on the number of particles in a substance
1. Freezing Point Depression: when any salt is added to
water, the freezing point of the water decreases.
Freezing point of pure water= 0 degrees C
Freezing point of salt water (NaCl solution)= -21°C (-6°F)
under controlled lab conditions
In the real world, on a real sidewalk, sodium chloride can
melt ice only down to about -9°C (15°F)

18. Molecular vs. Ionic
• When one mole of sucrose is dissolved in water,
one mole of particle is produced in solution:
C12H22O11(s) C12H22O11(aq)
• When one mole of an ionic substance is
dissolved in water, the results are different. The
ionic substance dissociates into individual ions:
NaCl(s) Na(aq) + Cl (aq)
• The greater number of ions, the lower the
freezing point.

19. Boiling Point Elevation
• When any salt is added to water, the
boiling point of the water increases.
• Boiling point of pure water= 100° C
• Boiling point of salt water solution
increases