Hit parade notes and review questions
Ch 15 Solutions
15.1 Forming Solutions, most of this is review.
You will be responsible for the entire section 15.1.
- Parts of a solution
A. Solubility
B. Solution Composition
C. Factors affecting the rate of dissolving
15.2 Describing Solution Composition.
You will be responsible for the entire section 15.2.
A. Mass percent
B. Solution composition – Morality
C. Dilutions
15.3 Properties of Solutions. You are only responsible for portions of this section.
A. Stoichiometry of Solution Reactions
D. Boling Point and Freezing Point – Colligative Properties
Practice problems for Ch 15
1. How many moles of each ion are present, per liter, in a solution that is labeled
“0.221M CaCl2”
2. Calculate the mass percent of calcium chloride in 1.00 g of calcium chloride in
19g of water.
3. What is the Molarity of a solution that has 4.25 g of CuCl2 in 125ml of water?
4. What mass in grams of NH4Cl is needed to prepare 450 mL of 0.251 M NH4Cl
solution?
5. What volume (in mL) of 0.25 M Na2SO4 solution is needed to precipitate all of
the barium as BaSO4 (s) from 125 mL of 0.15 M Ba(NO3)2 solution?
Ba(NO3)2 (aq) + Na2SO4 (aq)  BaSO4 (s) + 2 NaNO3 (aq)
6. Calculate the mass of AgCl formed, and the concentration of the silver ion
remaining in the solution, when 10.0 g of solid AgNO3 is added to 50.mL of
1.0X10-2 M NaCl solution. Assume there is no change in volume upon the
addition of the solid.
Answers
1. 0.221 mol Ca2+, 0.442 mol Cal- 2. 5.00% CaCl2
3. 0.253 M CuCl2
4. 6.04 g NH4Cl
6. 0.072 g AgCl, 1.2 M Ag+
5. 7.5 mL
Ch 16 – Acids and Bases
16.1 Properties of acids and bases
3 types of acids and bases
1. Arrhenius model
a. Acids produce H+ in solution
b. Bases produce OH- in solution
c. Reactions produce salt water
Example A:
Write out and balance the reaction between sulfuric acid and sodium hydroxide.
2. Bronstead-Lowry model
a. Acid – proton donor
b. Base – proton acceptor
c. Each BL acid or base has a conjugate base or acid pair
Example B:
Identify the BL acid and base with its conjugate pair in the following reactions.
NH3 + H2O  NH4+ + OH-
HCO3- + H2O H2CO3 + H3O+
3. Lewis model
a. Lewis acid – electron pair acceptor
b. Lewis base – electron pair donor
Example C:
Identify the Lewis acid and the Lewis base below.
H+ + NH3 NH4+
Answers to examples
A: H2SO4 + 2NaOH = Na2SO4 (aq) + 2HOH (l)
B: NH3 is the BL base and NH4+ is it conjugate acid, H2O is a BL acid and OH- is it s conjugate base. HCO3- is the BL acid and
H2CO3 is it conjugate base, H2O is a BL base and H3O+ is its conjugate acid.
C: H+ is the Lewis acid, NH3 is the Lewis base.
Acid strength:
Strong vs. weak
Water
Water undergoes auto-ionization to dissociate and produce acidic or basic ions freely
dissolved in solution.
Amphoteric: Water has both acid and base properties
H2O (l) + H2O (l)  H3O+ (aq) + OH-
Can you identify the BL acid and base demonstrated in water?
Equilibrium Constant: Kw = [H3O+] [OH-] = 1.0 x 10-14 at 25°C
No matter what water contains the Kw of any aqueous solution must have a product equal
to 1.0 x 10-14 at 25°C.
In class example
Calculate the [H=] concentration in a solution in which the [OH-] – 2.0 x 10-2 M.
Is the solution acidic or basic?
16.2 Determining the acidity of a solution
pH scale
pH = -log[H+]
Steps for calculator
Enter (-), press log, enter [H+]
pOH = -log{OH-]
pH + pOH = 14
In Class example
The pH of blood is 7.4. Is blood acidic or basic? What do you estimate is the [H+] ?
What is the pOH of blood?
Indicators are chemicals that change colors depending on the pH of a solution.
16.3 Titrations and buffers
Strong acid strong base reactions are often times called ______________________
With the following net ionic equation:
What is a titration, equivalence point, indicator, titration curve?
In class example:
Determine the volume of 0.100 M NaOH solution needed to titrate 50.0 mL of a 0.200 M
HNO3 solution.
Ch 17 Reaction rates and equilibrium
How can we affect the rate of a reaction?
How does a catalyst or an enzyme speed up a reaction?
What does it mean if a reaction is at a state of equilibrium?
Why does equilibrium occur?
Equilibrium constant, what does it tell us?
For the given reaction:
note, only gases can be included.
In class example
If K > 1 than the reaction favors the reactants
If K < 1 than the reaction favors theproducts
LeChatliers Principle
When you impose a change to a system at equilibrium it will shift in the direction to
reduce the effects of the change.
In Class Example
Practice Problems
1. What does activation energy for a reaction represent? How is the activation energy
related to whether a collision between molecules is successful? Draw out an energy
diagram for an exothermic reaction that includes the activation energy. How does the
addition of a catalyst affect the activation energy? What does the energy diagram look
like with the addition of a catalyst? Label all parts of your diagram. Describe the
reaction in the reverse and show it’s activation energy.
2. How do we recognize a system that has come to a state of equilibrium?
3. Write an equilibrium expression for the following reactions:
a.
P4 (g) + 6Br2 (g)  4Pbr3 (g)
b.
4Al (s) + 3O2 (g)  2Al2O3 (s)
4. Suppose the reaction system
CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (l)
Has already reached equilibrium. Predict the effect of each of the following changes on
the position of the equilibrium. Tell whether the equilibrium will shift to the right, will
shift to the left, or will not be affected. Explain why.
a. Any liquid water present is removed
b. CO2 is added to the system by dropping a chunk of dry ice into the reaction
vessel.
c. The reaction is performed in a metal cylinder fitted with a piston, and the piston is
compressed to decrease the total volume of the system.
d. Additional O2 (g) is added to the system from a cylinder of pure O2.
Answers
1. The minimum amount of energy needed for a reaction to occur. If the molecules do
not collide with enough energy to overcome the activation energy the reaction will not
proceed. See figure 17.2 The catalyst will decrease the activation energy. See figure
17.3 for a description of a catalyst. The reverse reaction will be the opposite as the
forward reaction, it will be endothermic.
2. rate of the forward reaction = rate of the reverse reaction
3a.
4a. no effect
3b.
4b. shifts left
4c. shifts right4d. shifts right
What is a spontaneous reaction?
How do we determine if a reaction is spontaneous?