Honors Chemistry
Unit 11, 12 and 13 Review
Concepts to know:
Unit 11: le chatlier’s principle
Boiling points
Boiling occurs when vapor pressure = outside pressure
Higher altitudes = less outside pressure = lower boiling point
Unit 12: suspensions, colloids, solutions (know how to tell the difference between them)
Homogenous mixture is the same thing as a solution
Tyndall effect
Solute-what is being dissolved
Solvent-dissolving medium
Like dissolves like (referring to bonding) - polar dissolves polar and ionic, nonpolar dissolves nonpolar
Miscible and immiscible
Solubility-tells how much solute a solvent can hold at a certain temperature
Unsaturated, saturated, and supersaturated solutions
Changes that affect how much solute can dissolve
At higher temperatures solvents can usually hold more solid solutes
At lower temperatures and higher pressures solvents can always hold more gas solutes
Factors that affect the rate of dissolving- temp, surface area, agitating
Heats of solution
Endothermic- energy is absorbed when solute dissolves, temp. decreases, positive ∆H
Exothermic- energy is released when solute dissolves, temp. increases, negative ∆H
Unit 13: Molarity, M, moles of solute/liter of solution
Molality, m, moles of solute/kg of solvent
Parts per million, ppm
Strong electrolytes- strong acids and soluble ionic- these conduct electricity strongly in solution (100% ions)
Weak electrolytes- weak acids and insoluble ionic- these conduct electricity weakly in solution (a few ions)
Nonelectrolytes- covalent compounds (exception: acids)-these do not conduct electricity in solution (no ions)
Know the seven strong acids- H2SO4, HClO4, HClO3, HNO3, HI, HCl, HBr- all others are weak
You will be given the solubility rules-these are for ionic compounds only and tell if they dissociate
completely or only a little bit.
If a salt is insoluble, it will form a precipitate (fall out of solution as a solid) in a reaction
Know how to tell how many ions and ionic salt will dissociate into
2+
2+
For example MgCl2 will dissociate into 3 ions MgCl2  Mg + 2Cl (one Mg and two Cl )
Practice problems:
1.
2.
A general equilibrium equation for boiling is: liquid + heat energy ↔ vapor
Is the forward or reverse reaction favored in each of the following cases?
a. The temperature of the system is decreased.
b. More molecules of the vapor are added to the system.
Reverse
reverse
c. liquid is added to the system
d. The temperature is increased
forward
forward
Solid CaCl2 does not conduct electricity, but it is considered to be an electrolyte. Explain.
An electrolyte will conduct electricity in solution. Solid calcium chloride does not have ions moving around so it
doesn’t conduct electricity, but once dissolved in water the ions are free to move so it will conduct electricity.
3.
Explain the following statements at the molecular level:
a. Generally a polar liquid and a nonpolar liquid are immiscible. Nonpolar molecules are too weak to pull polar
molecules apart and so they will not dissolve in one another.
b. Carbonated soft drinks taste flat when they are warmed. At higher temperatures, less gas can dissolve so it
leaves and the soda taste flat.
4.
An unknown compound is observed to mix with toluene, C 6H5CH3, but not with water.
a. Is the unknown compound ionic, polar covalent, or nonpolar covalent? Nonpolar covalent
b. Suppose the unknown compound is also a liquid. Will it be able to dissolve table salt? No
5.
Consider 500. mL of a 0.30 M CuSO4 solution.
a. How many moles of solute are present in this solution? 0.15 mol
b. How many grams of solute were used to prepare this solution? 24 g
90. g of CaBr2 are dissolved in 900. g of water. What is the molality of this solution? 0.50 m
6.
Match the type of mixture on the left to its representative particle diameter on the right.
solutions c
(a) larger than 1000 nm
suspensions a
(b) 1 nm to 1000 nm
colloids b
(c) smaller than 1 nm
7.
Identify the solvent in each of the following examples:
a. tincture of iodine (iodine dissolved in ethyl alcohol) ethyl alcohol
8.
9.
b. sea water water
A mixture has the following properties:
No solid settles out during a 48 hour period; the path of a flashlight beam is easily seen through the mixture; It appears to
be homogeneous under a hand lens but not under a microscope. Is the mixture a suspension, colloid, or true solution?
Of the following solution models shown at the particle level, indicate which will conduct electricity.
a. yes
b. no
c. yes
10. The solubility of KClO3 at 25°C is 10. g of solute per 100. g of H2O.
a. If 15 g of KClO3 are added to 100 g of water at 25°C with stirring, how much of the KClO 3 will dissolve? Is the solution
saturated, unsaturated, or supersaturated? 10 g; saturated
b. If 15 g of KClO3 are added to 200 g of water at 25°C with stirring, how much of the KClO 3 will dissolve? Is the solution
saturated, unsaturated, or supersaturated? 15 g; unsaturated
11. The heat of solution for KOH is -57.61 kJ/mole.
a. Is this exothermic or endothermic?
b. Will the temperature of the solution increase or decrease as it dissolves?
12. Describe the errors made by the following student in making a molar solutions. James needs a 0.600 M solution of KCl. He
measures out 0.600 g of KCl and adds 1 L of water to the solid.
He needs to measure 0.6 moles which is 44.8 g AND he needs to add water to make 1 L of solution (he added too
much water)
13. What is the molarity of a solution made by dissolving 2.0 mol of solute in 6.0 L of solvent? 0.33 M
14. CH3OH is soluble in water. What is the molality of a solution made by dissolving 8.0 g of CH3OH in 250. g of water? 1.0 m
15. Predict the solubility of the following compounds in water:
a.magnesium nitrate soluble
b. barium sulfate insoluble
c. calcium carbonate insoluble
d. ammonium phosphate soluble
16. 1.0 mol of magnesium acetate is dissolved in water.
a. Write the formula for magnesium acetate. Mg(C2H3O2)2
b. How many moles of ions are released into solution? 3 mol of ions
17. In the following two precipitation reactions, write the formula for the precipitate formed:
a. combining solutions of magnesium chloride and potassium phosphate magnesium phosphate, Mg3(PO4)2
b. combining solutions of sodium sulfide and silver nitrate silver sulfide, Ag2S
18. Write the equations showing the dissociation of the following compounds: How many ions do they produce in
solution?
a. Na3PO4(s)  3Na+ (aq)+ PO4 3- (aq)
b. iron(III) sulfate(s) Fe3+ (aq) + SO42- (ag)
19. In an aqueous solution of HCl, virtually every HCl molecule is ionized. True or False? Why? True, HCl is a strong acid so it
completely ionizes ( water is able to pull it apart)
20. Match the four compounds on the right to their descriptions on the left.
an ionic compound that is quite soluble in water b
an ionic compound that is not very soluble in water c
a molecular compound that ionizes in water a
a molecular compound that does not ionize in water d
(a) HCl
(b) BaCl2
(c) AgCl
(d) CCl4
21. Label the following as a nonelectrolyte, a weak electrolyte, or a strong electrolyte a.
CaBr2
b. H2SO4
c. NO2
d. H2O
e. Mg(OH)2
strong
strong
non
non
weak
f. MgSO4
g. iron (II) phosphate h. HNO2
i. HC2H3O2
strong
weak
weak
weak
22. What is the molarity of a solution if 321 g of Iron (II) chloride is dissolved in 205 mL of solution?
12.3 M
j. HI
strong
23. How many mL of a 3.6 M solution are needed to have 241.0 g of sodium hydroxide? 1700 mL
24. Explain each of the following
a. increasing the temperature of water speeds up the rate at which many solids dissolves.
Molecules will move faster so the solute and solvent will touch more often
b. increasing the surface area of a solid solute speeds up the rate at which it dissolves in a liquid solvent.
More of the solute and solvent will be in contact with each other.
25. Refer to the graph to answer the following questions:
a. What is the normal boiling point of ethanol? About 80 ⁰C
b. What would be the boiling point of water if the air pressure over the liquid were reduced to 60 kPa? about 85 ⁰C
c. What must the air pressure over ethanol be for it to boil at 50°C? about 30 kPa
d. Although water has a lower molar mass than ethanol it has a lower
vapor pressure when measured at the same temperature.
Why do you think water vapor is less volatile than ethanol? Strong intermolecular forces
26. Use this general equilibrium equation to answer the following questions:
reactants ↔products + heat energy
a. If the reaction shifts to the right, will the concentration of reactants
increase, decrease, or stay the same? decrease
b. If extra product is introduced, which reaction will be favored? reverse
c. If the temperature of the system decreases, which reaction will be favored? forward