CHEM 192 • Exam #4 • Fall 2012 • 100 points
Name:
See the Exam Reference Page for important information and notes.
Write the letter of the BEST choice in the blank provided (4 points each):
1. ________ Classify the reaction: 2 NaCl(l)  2 Na(s) + Cl2(g)
A. Synthesis
D. Double Replacement
B. Decomposition
E. Combustion
C. Single Replacement
2. ________ Which of the following compounds will precipitate if produced in a double replacement reaction?
A. AgNO3
B. Na2SO4
C. PbCl2
D. KCl
3. ________ What two states are you most likely to find ionic compounds in under ordinary lab conditions?
A. (s) or (aq)
B. (l) or (g)
C. (aq) or (l)
D. (aq) or (g)
4. ________ A reaction between aqueous magnesium bromide and chlorine gas would be what type of reaction?
A. Synthesis
D. Double Replacement
B. Decomposition
E. Combustion
C. Single Replacement
CLASSIFY each of the following reactions and BALANCE the equations (8 points each):
5. ____ Ca(s) + ____ HNO3(aq) 
____ Ca(NO3)2(aq) + ____ H2(g)
Reaction Type:
6. _____ CuCl2(aq) + _____ Na3PO4(aq) → _____ Cu3(PO4)2(s) + _____ NaCl(aq)
Reaction Type:
Write a complete, balanced equation for the following reaction, including state symbols (8 points):
7. Potassium metal is exposed to oxygen in the air, and forms the white solid, potassium oxide.
Write a complete, balanced equation for each of the following reactions, including state symbols:
(10 points each)
8. ____ C6H10O(g) + ____ O2(g) 
Reaction Type:
Combustion
9. ____ FeCl2 (aq) + ____ (NH4)3PO4(aq) 
Reaction Type:
10. ____ Mg(OH)2(aq)
Reaction Type:
Double Replacement (precipitation)
+ ____ HCl(aq)

Double Replacement (acid-base)
Predict the states of the products of the MOLECULAR EQUATION of the double replacement reaction,
balance the reaction, and write the NET IONIC EQUATION for the reaction (12 points):
11. _____NaBr(aq) + _____Pb(NO3)2 (aq)  _____NaNO3(
)
+ _____PbBr2(
)
Answer the following questions in the spaces provided.
12. (8 points) How many moles of sodium chloride is 1.72 x 1024 formula units of NaCl?
13. (8 points) How many moles of nickel (Ni) atoms are in 613.3g Ni?
14. (8 points) How many molecules of carbon dioxide are in 150 g carbon dioxide?
15. (8 points) A student collects the following data for the separation of salt and sand by the methods employed
in our experiment in lab (dissolving the salt in water, filtering off the sand, then evaporating the water from
the salt solution):
Unknown Number:
Mass of unknown sample:
Mass of evaporating dish:
Mass of filter paper:
Mass of evaporating dish and salt:
Mass of filter paper with the sand:
7A
2.44 g
28.92 g
1.25 g
30.38 g
2.48 g
Calculate the experimental mass % of salt:
16. (5 points) Another student carries out the experiment above and finds that the % salt and % sand add up to
well over 100%. What is the likely cause of the increased mass? (Assume all of the mass measurements
were taken correctly.)