UNIT 8 EXAM REVIEW
C/P: Chp 15 and 19
Honors: Chp 12, 14 and 15
Solutions plus Acid/Base Chemistry
2013
Chp 15
• Solutions contain a solute dissolved in a
solvent. They are always homogeneous!
• How do you know if a substance will
dissolve in water?
“Like dissolves like”
• Water is polar so nonpolar substances like
oil and other hydrocarbons will not dissolve
in water.
Concentrations
• Know the concentration units for molarity,
ppm and dilution.
Reminder:
Molarity = moles solute ÷ L of solution
Parts per million =
mass solute
x 1,000,000
mass of solvent
Dilution formula: M1V1=M2V2
Solubility and Solvation
• Three things that affect solubility/solvation:
• Agitation
• Temperature
• Surface area
***Plus Pressure for gases only
Colligative Properties
• Adding a solute (like salt) to water changes
the properties:
• Freezing point depression or lowering (< 0oC)
• Boiling Point Elevation (>100oC)
• Vapor Pressure Lowering – less molecules in
gas phase. This is why BP increases.
Remember: CP depend on the number of
particles in solution, not the type of particles
C12H22O11=1 particle, NaCl=2 particles and
CaCl2= 3 particles
Sample Problems
1. If the solubility of NaCl is 30g/100g H2O, how
many grams can be dissolved in 250 g of
water?
2. Will these substances dissolve in water?
NaCl, vegetable oil, gasoline- C8H18
3. What is the molarity of a solution that contains
250 g of NaCl in 500 mL of water?
Sample Problems
1. If the solubility of NaCl is 30g/100g H2O, how
many grams can be dissolved in 250 g of
water? 75g NaCl
2. Will these substances dissolve in water?
NaCl, vegetable oil, gasoline- C8H18
3. What is the molarity of a solution that contains
250 g of NaCl in 500 mL of water? 8.56M NaCl
Sample Problems
4. Why did you add rock salt to the ice in the Ice
Cream Lab?
5. Name 3 things that would decrease the
solubility of sugar in tea?
6. If the attractive forces between solid particles
are stronger than those between the solid and
water, would the solid dissolve?
Sample Problems
4. Why did you add rock salt to the ice in the Ice
Cream Lab? To lower the temperature so ice
cream would solidify
5. Name 3 things that would decrease the
solubility of sugar in tea? Don’t stir it, cool it
down and use sugar cubes instead of
granulated sugar.
6. If the attractive forces between solid particles
are stronger than those between the solid and
water, would the solid dissolve? Nope
Chp 19
• H+ acid
• OH- base
• H2O neutral
pH = 0 - 6.9 blue to red
pH = 7.1 -14 red to blue
pH = 7 no change to litmus
• Neutralization reaction:
equal amounts of acid and base
H+ + OH-
H2O
Strong vs Weak Acids & Bases
• Strong acid and bases dissociate
(separate) completely – strong electrolyte
• Stg acid = HCl
• Stg Base = NaOH
• Weak acid and bases do not dissociate
completely – weak electrolyte
• Wk acid: CH3COOH
• Wk base: NH3
pH and pOH Scale
• Goes from 0-14
• 0 strong acid, 7 neutral, 14 strong
base
• pOH = 14- pH
• If pH = 2 then pOH = 12
Sample Questions
1. What is the formula of the hydronium ion?
2. What does water contain?
3. A substance has a pH of 5.5:
a) Classify it as a strong/weak acid or base.
b) What is the pOH of the solution?
Sample Questions
1. What is the formula of the hydronium ion?
H3O+
2. What does water contain?
Water molecules, hydronium ions and
hydroxide ions
3. A substance has a pH of 5.5:
a) Classify it as a strong/weak acid or base.
b) What is the pOH of the solution?
14 - 5.5 = 8.5