Download Exam 2 Review - Iowa State University

Exam 2 Review
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Lilli Howard
Chem 177 (BC)
Dr. Irmi
10/3/13
Determining Empirical and Molecular Formulas (3.5)
1. A compound contains only the elements Al and O. Its elemental compositions is
determined to be 53.0% aluminum and 47.0% oxygen. The mass of one mole of the
compound is 102 g. What is the empirical formula of the compound? What is the
molecular formula?
Chemical Equations: Mass and Mole Relationships (3.6-3.7)
1. How many moles of Al2O3 are produced when 0.50 mol Al reacts with an excess of
PbO2? The balanced chemical equation is:
4 Al (s) + 3 PbO2 (s)  2 Al2O3 (s) + 3 Pb (s)
2. Calculate the percent yield of the reaction given that 205 g of Al(OH)3 reacts with
751 g of H2SO4 to yield 252 g of Al2(SO4)3.
2 Al(OH)3 (s) + 3 H2SO4 (aq)  Al2(SO4)3 (s) + 6 H2O (l)
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Aqueous Solution: Electrolytes, Acids, and Bases (4.1, 4.3)
1. Solvent: ___________________________________________________
2. Solute: ____________________________________________________
3. Strong Electrolytes: _________________________________________________
4. Weak Electrolytes: __________________________________________________
5. Nonelectrolytes: ___________________________________________________
Identify each of the following as an acid or base and writes its reaction with water:
a. HF (g)
b. H2SO4 (l)
c. NaOH (s)
d. Ba(OH)2 (s)
Precipitation Reactions: Ionic Equations (4.2)
1. Identify the following salts as soluble or insoluble in water:
a. Fe(NO3)3
b. PbCl2
c. CaBr2
d. BaSO4
e. Na2SO4
2. Write a net ionic equation for the following reaction:
NaCl (aq) + AgNO3 (aq)  AgCl (s) + NaNO3 (aq)
3. Complete the following reaction and write the net ionic equation
Pb(NO3)2 (aq) + KBr (aq) 
Oxidation and Reduction: Oxidation Numbers and Activity Series (4.4)
Oxidation: ___________________________________________________________
Reduction: ___________________________________________________________
A Few General Rules
1. Oxidation number of an element in its elementary or uncombined state is 0.
2. In an ionic compound, the oxidation number of a monatomic ion is the same
as its charge.
3. Certain elements almost always have the same oxidation number.
a. Group 1A elements = +1
b. Group 2A elements = +2
c. Group 3A elements = +3
d. F, Cl, Br, I = -1 in binary compounds with metals
e. H = +1 (-1 in metallic hydrides)
f. O = -2
4. The sum of oxidation numbers of all atoms in a compound equal the charge of
that compound
1. Identify the oxidation number of each individual atom in the following equation.
a. Which atom is being oxidized? Reduced?
Zn (s) + H2SO4 (aq)  ZnSO4 (aq) + H2 (g)
2. Using the Activity Series, write balanced chemical equations for the following reactions:
a. Iron metal is added to a solution of copper (II) sulfate
b. Hydrogen gas is passed over mercuric oxide
Concentrations of Solutions (4.5)
1. Finish the equation: Molarity = ______________
2. What is the molarity of an ethanol solution containing 10.0 g of ethanol in water with a
total volume of 100 mL?
3. How many K+ ions are there in 200.0 mL of a 0.20 M K2SO4 solution?
4. What is the molarity of a solution of NaOH formed by diluting 125 mL of a 3.0 M NaOH
solution to exactly 500 mL?
Solution Stoichiometry (4.6)
1. What volume of 0.250 M HCl is required to react completely with 25.00 mL of 0.500 M
NaOH?
2. What is the molarity of a solution of H3PO4 if 50.00 mL of it is titrated with 25.86 mL of
0.1201 M NaOH? (Assume all 3 hydrogens in H3PO4 react with NaOH)
3. A 20.05 mL sample of vinegar (aqueous solution of HC2H3O2) has a density of 1.061
g/mL. The vinegar is titrated completely with 40.10 mL of 0.4100 M KOH. What is the
percentage by mass of acetic acid in the vinegar?
Thermodynamics: The First Law and Internal Energy Changes (5.1, 5.2)
W=fxd
PE = mgh
KE = ½ mv2 E = kQ1Q2/d ΔE = q + w
1. Calculate the velocity of an electron who’s mass is 9.107 x 10-28 g and whose kinetic
energy is 1.585 x 10-17 J.
2. Calculate the internal energy change in a system in which the following changes occur:
a. 100 g of MgO (s) is heated from 50 °C to 100°C, a process that requires 870 J
i. No work is done
b. A gas expands slowly while heating and does 200 J of work and gains 350 J of
heat.
3. An ice cube melts.
a. What is the system?
b. What are the surroundings?
c. Exothermic or endothermic?