Dr. Overway
PRACTICE EXAM II
CHEM 161-01
October, 2003
Instructions: Do not open this test booklet until you are instructed to do so.
Show your work in order to receive partial credit. Keep track of units and use the correct significant
figures. The following information may be useful during the exam.
Here are some things you may need.
Formal Charge = # of valence e - - # of non-bonding e - - # of bonds
OR
Formal Charge = # of valence e - # of non-bonding e - ½ (# of bonding e - )
Avagadro’s number = 6.022×1023 things/mol
R=0.08206 (L•atm)/(K•mol)
molal = moles solute / kg solvent
Molarity = moles solute / L solution
M1V1 = M2V2
n= moles=mass/MM=m/MM
Kb (water) = 0.512 °C kg/mol
Kf (water) = 1.858 °C kg/mol
∆Tf = Kf cm ·i
∆Tb= Kb cm ·i
π= MRT·i
CHEM 161
Practice EXAM II
Name
1. Name or provide a formula for the following chemical compounds and identify which is a covalent
compound or an ionic compound.
Name
Formula
Ionic or covalent?
Ca(OH)2
copper(II) iodide
nitrogen trifluoride
ClF5
magnesium bromide
2. Name or provide a formula for the following chemical compounds.
Name
Formula
ClO4 hydrogen carbonate ion
C5H12
HIO2
fluorous acid
MnO4FeCl3
phosphorus pentafluoride
3. (6 pts) What is the % by weight of C in C8H18? (use at least 4 significant figures with all atomic
weights)
.
4. A) What mass of CO2 can be produced from the combustion of 10.8 kg of hexane (C6H14) and
18.20 kg of oxygen (O2)? Write out the balanced reaction for full credit.
B) What mass of the excess reagent is left?
5. Match the terms below with their definitions.
Terms
____ spectator ion
____ Na+, NH4+, and K+
____ NO3- and CH3COO- (C2H3O2-)
____ precipitate
____ soluble salt
____ net ionic reaction
____ insoluble salt
Definitions
A) a solid that forms when a reaction occurs in a solution
B) anions that always form soluble salts
C) an ionic compound that does not dissolve to any great
extent
D) cations that always form soluble salts
E) an ion is solution that does not change its state and is not
involved in the reaction
F) a reaction in which all spectator ions have been removed;
shows only the species involved in the reaction
G) an ionic compound that dissolves in solution to form ions
6. The name of ClF5 is: (circle the best answer)
a. chloropentafluoride
b. chlorine fluoride
c. pentafluorochloride
d. chlorine pentafluoride
7. In the following reactions, circle the limiting reagent. You must show all of your work to get any
credit.
A) 2 NO3- (aq) + H2O(l) → N2O(g) + 2 O2 (g) + 2 OH-(aq)
B) 2 Bi + 3 F2 → 2 BiF3
with 10 mol of NO3- and 10 mol of H2O
with 10 g of Bi and 10 g of F2
8. Draw the most stable Lewis structure for PO43-. Calculate and list the formal charges of all of the
atoms in the final, stable structure.
9. Rank the polarity (or electronegativity difference) of the following bonds from least polar to the
most polar.
H-Br , H-F , H-Cl , H-I
_____ < _____ < _____ < _____
10. Rank the polarity (or electronegativity difference) of the following bonds from least polar to the
most polar.
H-N , H-C , H-F , H-H
_____ < _____ < _____ < _____
11. Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by
dissolving 78.6 g of KF in enough water to produce 225 mL of solution.
12. Circle the aqueous solution that should have the highest boiling point. Explain your answer.
A. 1.0 M KNO3 (electrolyte)
B. 0.75 M NaCl (electrolyte)
C. 0.75 M CuCl2 (electrolyte)
D. 2.0 M C12H22O11 (sucrose, non-electrolyte)
13. (6 pts) Using one of the molecular orbital diagrams below, fill in the electrons and calculate the bond
order of the molecule N2+
bond order =
14. Dimethylglyoxime, DMG, is an organic compound used to test for aqueous nickel(II) ions. A
solution prepared by dissolving 65.0 g of DMG (a non-electrolyte) in 375 g of ethanol boils at
80.3°C. What is the molar mass of DMG? (Kb = 1.22 °C /molal, boiling point of pure ethanol =
78.5°C)
15. What mass of BaSO4 would be produced by mixing 1.37 L of a 2.00-M Na2SO4 solution with 2.10 L
of a 1.50-M Ba(NO3)2 solution? The two solutions react according to the following net ionic
equation:
Ba2+(aq) + SO42-(aq)
BaSO4(s)