EXAM 4 REVIEW TOPICS
EXAM 4 REVIEW TOPICS
General Information

The exam will be administered on Wednesday, May 4th in Room 2210. Exam Start Time = 8:05 AM
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You will have the entire class period to take this exam.
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There is only “one part” to this test, being entirely calculations.
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You may use your calculators and the Exam 4 Reference Packet for the entire exam.
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Unless otherwise stated, you must use dimensional analysis form in your calculations.
The following material will NOT be on Exam 4

Naming acids

Intermolecular Forces
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%(w/w)…except maybe as extra credit.
Exam Questions
Unless otherwise stated, all calculations must be shown in dimensional analysis form.

Two Questions: Avogadro’s Number
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
Write the conversion factor (equality form) between one mole of particles and number of particles.


Avogadro’s Number Include representative particles in the final answer.
1A)
What is the representative particle for potassium chloride?
2 points; Max Time (1 min)
1B)
Write the conversion factor between 1 mole of potassium chloride and the number potassium chloride particles.
5 points; Max Time (1 min)
1c)
Use the conversion factor from Question 1B to calculate the number of potassium chloride particles present in
0.0257 moles of potassium chloride. 10 points; Max Time (4 min)
Page 1 of 10
EXAM 4 REVIEW TOPICS

Two Questions: Molar Mass
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
Calculate molar mass (all work shown, show units through every step)
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
Be able to write the molar mass as a conversion factor (equality form)
2A)
Calculate the molar mass of Fe2(Cr2O7)3?
You must show work (no dimensional analysis) for this question. In any question after this, you do not need to
show your work to calculate molar mass. 15 points; Max Time (2 min)
2B)
Write the molar mass in conversion factor form (equality form).
5 points; Max Time (30 s)
2c)
Convert 1.519 grams of Fe2(Cr2O7)3 to moles. 10 points; Max Time (4 min)
Page 2 of 10
EXAM 4 REVIEW TOPICS

Four Questions: Molarity
OMIT
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Rearrange the Molarity equation (show work) to convert solve for either “moles of solute” or “liters of soln”
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
When given the molarity, be able to write the molarity as a conversion factor (equality form)


Given mass and volume, calculate the molarity of a solution


Either:


You will be given the molarity and the moles (or mass). Solve for liters of solution.


You will be given the molarity and the volume. Solve for moles of solute (or mass).
4)
Calculate the concentration (molarity) of a solution that is prepared by dissolving 50.00 grams of sodium
hydroxide in 200. mL of water. The molar mass of sodium hydroxide, NaOH, is 40.00 g/mol. (Make sure to write
the molarity equation before plugging in values.) 16 points; Max Time (5 min)
5A)
A solution is 0.240 M NaCl. Write this value in conversion factor form (equality).
5 points; Max Time (30 s)
5B)
Determine the mass (in grams) of NaCl present in a 12.2 L the 0.240 M NaCl solution described in Question 5A.
Use the conversion factor from Question 5A to help solve this problem. 14 points; Max Time (5 min)
Page 3 of 10
EXAM 4 REVIEW TOPICS
CHEM 110 (BEAMER)
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Two Questions: One-Step Conversions.


Calculation between particles and moles (either direction)
Omit: already did this in Question 1C
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
Calculation between moles and mass (either direction)
Omit: already did this in Question 2C
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Two Questions: Multi-Step Stoichiometry
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
Initial Information for KNOWN: mass (or density and volume) or particles or molarity and volume
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
For the UNKNOWN, calculate: mass (or volume using density) or particles or molarity or volume
INFORMATION FOR QUESTION 6
169.87 g/mol
Reaction 6:
Given:
6)
3 AgNO3(aq)
3.250 L
0.400 M
136.09 g/mol
+
K3PO4(s)
418.57 g/mol

Ag3PO4(s)
101.10 g/mol
+
3 KNO3(aq)
UNK
Calculate the number of potassium phosphate formula units required to react with the given amount of silver nitrate. 18 points. Max Time (7 min)
Page 4 of 10
EXAM 4 REVIEW TOPICS
CHEM 110 (BEAMER)
INFORMATION FOR QUESTION 7
29.88 g/mol
Reaction 7:
Given:
7)
Li2O(s)
250.0 g
18.02 g/mol
+
H2O(s)
23.95 g/mol

2 LiOH(aq)
0.800 M
?
Assume an XS amount of water. Calculate the volume (in L) of 0.800 M lithium hydroxide solution that can be prepared from 250.0 grams lithium oxide.
18 points; Max Time (7 min)
Page 5 of 10
EXAM 4 REVIEW TOPICS
CHEM 110 (BEAMER)
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Four Questions: Theoretical Yield (originally, I said “five” questions. Evidently, I can’t count).


When given information for two reactants, determine the theoretical yield


When given the actual yield, determine the percent yield
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Label the LR and the XS


Determine the remaining amount of XS
INFORMATION FOR QUESTION 8A – 8D
163.94 g/mol
Reaction 8:
Given:
2 Na3PO4(s)
50.00 g
129.60 g/mol
+
3 NiCl2(aq)
366.02 g/mol

Ni3(PO4)2(s)
58.44 g/mol
+
6 NaCl(aq)
0.250 M
2.000 L
8A)
Calculate the theoretical yield (in grams) of nickel(II) phosphate. Label LR and XS, and rewrite the value for the theoretical yield in the box below.
38 points; Max Time (10 min)
8B)
Remember to label the LR and the XS. 4 points; Max Time (30 s)
Page 6 of 10
EXAM 4 REVIEW TOPICS
CHEM 110 (BEAMER)
INFORMATION FOR QUESTION 8A – 8D
163.94 g/mol
Reaction 8:
Given:
2 Na3PO4(s)
50.00 g
129.60 g/mol
+
3 NiCl2(aq)
366.02 g/mol

Ni3(PO4)2(s)
58.44 g/mol
+
6 NaCl(aq)
0.250 M
2.000 L
8C)
A student performs this experiment and obtains an experimental (actual) yield of 49.22 g Ni 3(PO4)2(s). Calculate the percent yield.
12 points; Max Time (5 min)
8D)
Calculate the moles of leftover XS. 32 points; Max Time (10 min)
Page 7 of 10
EXAM 4 REVIEW TOPICS
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Two Questions: Percent Yield
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
When given the percent yield, write the value as a conversion factor
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
Use the conversion factor to calculate either the theoretical yield or the actual yield
CHEM 110 (BEAMER)
9A)
A student performs an experiment, and the %-yield of the main product, H2O, is 95.2%. Write a conversion factor for this percentage (equality form)
Assume that the main product was measured in units of grams. 5 points; Max Time (1 min 30 s)
9B)
Using the conversion factor from Question 9a, calculate the theoretical yield (in grams) of water if the experimental (actual) yield was 17.31 grams H2O
10 points; Max Time (4 min)
Page 8 of 10
EXAM 4 REVIEW TOPICS

10)
CHEM 110 (BEAMER)
One Question: %-by-mass (substance will have three elements)
Determine the %-by-mass of each element in Mg3N2. Show the setup just like the practice problems in class.
36 points. Max Time (7 min)
(Omitted)

Two Questions: Write a percent-by-mass value as a conversion factor and use it in a calculation. Omitted

Note: I am omitting this question for the test. But, you might see one like it on the Final Exam.

Question: Compound X is 45.3% Ca by mass. Write a conversion factor for this value, and determine the mass of
calcium in a 7.1-g sample of Compound X. 5 points (for the conversion factor); 10 points (for the
calculation); Max Timing (4 min)
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Page 9 of 10
EXAM 4 REVIEW TOPICS
CHEM 110 (BEAMER)
11)
A compound is 52.14% carbon, 7.31% hydrogen, and 40.55% nitrogen by mass. Determine the empirical
formula of this compound. 60 points. Max Time (10 min)
12)
The molecular mass of a substance is 80.10 g/mol. The empirical formula for the substance is C2H2N. Determine
the molecular formula for this substance. 13 points; Max Time (4 min)
Page 10 of 10