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Name______________________________________
Student ID Number___________________________
TA Name___________________________________
Lab Section_________________________________
Fall 2015 - Enderle
CHEMISTRY 2A
Exam I
Multiple Choice (circle one)
Instructions:
CLOSED BOOK EXAM! No books, notes, or additional scrap paper are
permitted. All information required is contained on the exam. Place all work
in the space provided. If you require additional space, use the back of the
exam.
(1) Read each question carefully.
(2) There is no partial credit for the problems in Part I and Part II. You will
lose 10 points if you do not circle your multiple choice answers on the
front page or if you do not write your TA’s name or section in the space
above.
(3) The last page contains a periodic table and some useful information.
You may remove this for easy access.
(4) Graded exams will be returned in the laboratory sections next week.
(5) If you finish early, RECHECK YOUR ANSWERS!
1.
A
B
C
D
E
2.
A
B
C
D
E
3.
A
B
C
D
E
4.
A
B
C
D
E
5.
A
B
C
D
E
6.
A
B
C
D
E
7.
A
B
C
D
E
8.
A
B
C
D
E
9.
A
B
C
D
E
10.
A
B
C
D
E
1–12. 36 points
11.
A
B
C
D
E
13–15. 14 points
12.
A
B
C
D
E
U.C. Davis is an Honor Institution
Possible Points
16–17. 24 points
18. 09 points
19–20. 20 points
21. 10 points
Total Score (113)
Points
Exam I
Page 2 of 9
Part I: Multiple Choice
Circle the correct answer here and on the cover – No partial credit (3 points each)
1.
How many hydrogen atoms are present in 3.00 millimoles of water?
A. 3.61 x 1019 B. 3.61 x 1021 C. 1.81 x 1019 D. 1.81 x 1021 E. 3.61 x 1024
2.
Calculate the percent mass of nitrogen in dinitrogen pentoxide.
A. 17.5 % B. 46.7 % C. 21.9 % D. 25.9 % E. 100.0 %
3.
Which of the following reactions is an acid-base neutralization?
A. 3 Cu (s) + 8 HNO3 (aq) à 3 Cu(NO3)2 (aq) + 2 NO (g) + 4 H2O (l)
B. Na2S (aq) + 2 KNO3 (aq) à 2 NaNO3 (aq) + K2S (aq)
C. HNO3 (aq) + KOH (aq) à KNO3 (aq) + H2O (l)
D. 2 Fe (s) + 6 HCl (aq) à 2 FeCl3 (aq) + 3 H2 (g)
E. Pb(ClO4)2 (aq) + 2 NH4Cl (aq) à PbCl2 (s) + 2 NH4ClO4 (aq)
4.
What multipliers are needed for the three respective simultaneous reactions below, in order
to obtain this overall reaction: CH4 (g) + NH3 (g) → HCN (g) + 3H2 (g)?
Find the multipliers (α, β, γ). ℓ→
[N2 (g) + 3 H2 (g) → 2 NH3 (g)] x α
[C (s) + 2 H2 (g) → CH4 (g)] x β
[H2 (g) + 2 C (s) + N2 (g) → 2 HCN (g)] x γ
A. -1, -½, 1
B. -½ , -1, ½
C. 1, -2, -1 D. -2, -1, 2 E. -1, -2, 1
5. Two cations, Ba2+ and Ag+, are mixed with two anions, Cl- and OH-. Which pair will be the
most soluble (i.e., no precipitate)?
A. AgOH
B. AgCl C. Ba(OH)2 D. BaCl2 E. BaAgCl
6. Main group elements are those in groups ________.
A. 1 and 2 B. 1, 2, and 13 to 18 C. 13 to 18 D. 1 and 18
E. 3 to 12
7. Niacin is also known as Vitamin B3. (See molecule to the right). How many H atoms
are in one molecule of niacin?
A. 1 B. 5 C. 9 D. 10 E. 11
8. 0.250 M solution of OH- was made by reducing the volume of a Ca(OH)2 stock solution by
four. What was the concentration of the Ca+ in the stock solution?
A. 1.00 M
B. 1.50 M
C. 3.50 M
D. 0.500 M
E. 2.00 M
9. Which of the following is not a base?
A. NaOH B. CsOH C. NH4OH
D. C2H5OH
E. Sr(OH)2
10. Which of the following represents the highest temperature?
A. 20°F
B. 0°C C. 0 K
D. 270 K
E. 0°F
Exam I
Page 3 of 9
11. An element has 5 stable isotopes. The mass and percentage of each are:
69.9243
20.52%
71.9217
27.43%
72.9234
7.76%
73.9219
36.54%
75.9214
7.76%
The element is which of the following?
A. As
B. Se C. Ge D. Ga
E. Zn
12. Which of the following is most likely a strong electrolyte?
A. A solid ionic compound
B. A weak acid
C. A molecular compound
D. A strong base
E. Liquid water
Part II: Short Answer
Fill in the blank
13. (4 points) Consider the molecule [Co(NO2)(NH3)5]2+.
What is the oxidation state of Co?
How many electrons are in this molecule?
14. (4 points) Balance using whole numbers. One coefficient is already done for you.
____ K3[Fe(SCN)6] + ____ Na2Cr2O7 + ____ H2SO4 →
____ Fe(NO3)3 + ____ Cr2(SO4)3 + ____ CO2 + ____ H2O + ____ Na2SO4 + 3 KNO3
15. (6 points) Write the balanced chemical equation for the following reactions (include states
for each species).
A. The decomposition of solid sodium carbonate into solid sodium oxide and carbon dioxide
B. The net ionic equation for the reaction between aqueous BaCl2 and CuSO4.
Exam I
Page 4 of 9
16. (12 points) Fill in the blanks of the table giving the chemical name or chemical formula.
Chemical Formula
Chemical Name
As4O10
tin(IV) or stannic ion
oxalic acid
Fe2(HPO4)3
NH4I
CH3(CH2)8CH3
17. (12 points) Fill in the blank: in the column marked “Answer,” fill in the answer that best
describes the statement or question. Most answers are one-word and two are a few words long.
The first one is done for you as an example.
Answer
Chadwick
Statement
1. This person performed a series of experiments leading to the discovery
of the uncharged particle in the nucleus, later called the neutron.
2. According to this law, water is H2O, not H4O2 or H3O1.5.
3. What appears in consecutive reactions, but not in an overall reaction?
4. This type of compound can be defined as a hydroxide ion donor.
5. This law was described by Lavosier when he realized that the mass
before and after a reaction was the same.
6. This scientist used the Oil Drop experiment to find the charge of an
electron to be 1.6022 x 10-19 C.
7. This scientist coined the term X-ray to describe radiation from a CRT.
Exam I
Page 5 of 9
Part III: Long Answer
Please show all work – Partial credit – Use the correct number of significant figures
18. (9 points total) Consider the balanced chemical equation below:
3 CuSO4 (aq) + 2 Na3PO4 (aq) → Cu3(PO4)2 (s) + 3 Na2SO4 (aq)
Consider the mixing of 1.00 L of 3.00 M CuSO4 and 1.00 L of 3.00 M Na3PO4. Assume the
reaction goes to completion and solute volumes are additive. Put your answer in the box
provided.
A. (5 points) Calculate the mass of Cu3(PO4)2 produced (in grams).
Mass Cu3(PO4)2
produced =
B. (4 points) Calculate the concentration (in molarity) of Cu2+ and SO42- ions in solution.
Molarity
of Cu2+ =
Molarity
of SO42– =
Exam I
Page 6 of 9
19. (7 points) The percent yield of oxygen for the following reaction is 65.0%. How many grams
of KClO3 are needed to produce 32.0 g of O2? Put your answer in the box provided.
2 KClO3(s) → 2 KCl(s) + 3 O2(g)
g KClO3 =
20. (13 total points) Given the reaction: P4 (s) + H2O (l) → PH3 (g) + H3PO4 (aq)
A. (2 points) Which species is oxidized? Which species is reduced?
Oxidized:
Reduced:
B. (4 points) Balance the reduction half reaction (acidic solution). Include state symbols.
C. (4 points) Balance the oxidation half reaction (acidic solution). Include state symbols.
D. (3 points) Give the overall reaction below (acidic solution). Include state symbols.
Exam I
Page 7 of 9
21. (10 points total) Lauric acid, as a component of triglycerides, comprises about half of the
fatty acid content in coconut oil. The mass percent composition of lauric acid is 71.95% C,
12.08% H, and 15.97% O. The molar mass of lauric acid is 200.36 g/mol. Write your answers in
the appropriate box below.
A. (8 points) What is the empirical formula of lauric acid?
Empirical
Formula
B. (2 points) What is the molecular formula of lauric acid?
Molecular
Formula
Exam I
Page 8 of 9
Exam I
Avogadro’s number = 6.022 x 1023 / mol
K = C + 273.15
M1 V 1 = M2 V 2
d = m/V
2.54 cm = 1.00 in (exact)
Page 9 of 9
F = 9/5 C + 32
Solubility Rules:
Compounds that are soluble or mostly soluble
• Group 1, NH4+, chlorates, acetates, nitrates
• Halides (except Pb2+, Ag+, and Hg22+)
• Sulfates (except Ca2+, Sr2+, Ba2+, Pb2+, and Hg22+)
Compounds that are insoluble
• Hydroxides, sulfides (except above rule, and group 2 sulfides)
• Carbonates, phosphates, chromates (except above rules)