1. Aqueous Reactions and Solution Stoichiometry
Honors Chemistry
Mr. Kinton
Enloe High School

2. Colligative Properties
Properties of a solvent that depend on the total concentration of the solute particles present
Vapor pressure, boiling-point elevation, freezing-point depression, and osmotic pressure

3. Vapor Pressure
Pressure exerted by a vapor on a liquid in a closed container at equilibrium
Nonvolatile: a substance with no measurable vapor pressure
Volatile: substance with a measurable vapor pressure
Vapor pressure will be lowered with the addition of a nonvolatile solute to a solvent

4. Boiling-Point Elevation
When additional solute is added, the boiling point of a solution will increase
Depending on the type of solute will determine how much the boiling point will increase
Strong electrolytes increase boiling point more than a nonelectrolyte

5. Freezing-Point Depression
When a solute is added to a solution that will cause the freezing point to decrease
Just like with boiling-point elevation, the type of solute in the solvent influences how much freezing point changes

6. Osmotic Pressure
The net movement of solvent molecules from the less concentrated solution to the more concentrated solution
Osmotic pressure is the pressure exerted in a solution to prevent the movement of solvent

7. Net Ionic Equations
Double replacement reactions occur in aqueous solution
Molecular Equation: equation that shows the complete chemical formulas of the reactants and products without indicating ionic character
Complete Ionic Equation: equation that shows all soluble strong electrolytes as ions
Spectator Ions: Ions that appear in identical forms on the reactants and products side. These ions play no direct role in the reation

8. Net Ionic Equations
Net Ionic Equations: Equation that omits the spectator ions leaving only the ions and molecules directly involved in the reaction
If every ion in a complete ionic equation is a spectator, then no reaction occurs

9. Net Ionic Equations Procedure for writing net ionic equations:
Write a balanced molecular equations for the reaction
Rewrite the equation to show the ions that form in solution when each soluble strong electrolyte dissociates or ionizes into it ions
Only strong electrolytes dissolved in aqueous solution are written in ionic form
Identify and cancel spectator ions

10. Net Ionic Equation Pb(NO3)2(aq)+2KI(aq)PbI2(s)+2KNO3(aq)
CaCl2(aq)+Na2CO3(aq)CaCO3(s)+2NaCl(aq)
Ba(OH)2(aq)+HC2H3O2(aq)Ba(C2H3O2)2(aq)+H2O(l)

11. Autoionization of Water
Process where one molecule of water donates a proton to another water molecule
H2O(l) + H2O(l) H3O+(aq) + OH-(aq)
H3O+: Hydronium ion
This process happens rapidly and the molecules of water do not stay ionized for long
This process occurs at equilibrium, which means the forward and reverse process occur at the same rate

12. Equilibrium Expression and the Ion Product Constant
For any reaction at equilibrium, an equilibrium expression can be written to show which side of the reaction is favored
For water, it has an ion product constant (Kw) that equals 1.0 × at 25oC
This means that the reactants in the autoionization of water are extremely favored
Kw = [H3O+][OH-]

13. Equilibrium Expression and the Ion Product Constant
The Kw for water can be used to describe any dilute aqueous solution
This will allow us to calculate the [H+] or the [OH-] depending on what we know
When [H+]=[OH-], the solution is neutral
When [H+]>[OH-], the solution is acidic
When [H+]<[OH-], the solution is basic

14. Solving Equilibrium Expressions
Determine if the following solution is acidic, basic, or neutral and solve for the concentration of the missing ion:
[H+] = 4 × 10-9 M
[OH-] = 1 × 10-7 M
[OH-] = M

15. Characteristics of Acids and Bases
Ionize in water to produce H+ (Arrhenius)
Begin with H
Sour taste
Cause skin burns
Turn litmus paper red and colorless in phenolphthalein
Ionize in water to produce OH- (Arrhenius)
Ends with OH
Bitter taste
Feel slippery or soapy
Turn litmus paper blue and pink in phenolphthalein

16. pH Scale
Since the concentration of H+ is usually very small we express that concentration using the pH scale
pH = -log[H+] or –log[H3O+]
pH = 7 is a neutral solution
pH < 7 is an acidic solution
pH > 7 is a basic solution
A change in [H+] by a factor of 10 causes a change in pH of 1
[H+] = 10^-pH

17. pH Scale
In a sample of lemon juice [H+] = 3.8 x M. What is the pH?
A sample of freshly pressed apple juice has a pH of Calculate the [H+].

18. Other “p” Scales
The concentration of hydroxide ion can be measured using pOH
pOH = -log[OH-] and [OH-] = 10^-pOH
pH + pOH = 14

19. Solution Stoichiometry
Specific application of stoichiometry where concentration can be used as a conversion factor
Solution stoichiometry is no different than regular stoichiometry
Just remember our conversion factors

21. Solution Stoichiometry
How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of M HNO3?
How many liters of M HCl are needed to react completely with mol of Pb(NO3)2, forming a precipitate PbCl2?

22. Titrations
Technique used to determine the concentration of a solute in solution
This is done by using a solution with a known concentration (standard solution)
Titrations can be used for acid-base reactions, precipitation reactions, and oxidation-reduction reactions

23. Titrations
Equivalence point: the point at which stoichiometrically equivalent quantities are brought together
Indicators: used to help chemists identify when the equivalence point has been reached
When the indicator changes that signals the end point of the titration which is usually close to the equivalence point

24. Titrations
How many grams of chloride ion are in a sample of the water if 20.2 mL of M Ag+ is needed to react with all of the chloride in the sample?
45.7 mL of M H2SO4 is required to neutralize a 20.0 mL sample of NaOH solution. What is the concentration of NaOH?