CHEM 3: Midterm Exam 1: Spring 2016 (100 points)
Name: ___________________________________
INSTRUCTIONS: On the FRONT and BACK of the scantron, fill out your name and 7-digit student ID. Fill in this
information from left to right in the provided fields, and BUBBLE IN the values on the scantron. 1 point will be
deducted from your exam grade for incomplete or erroneous filling of the scantron. Please read each question
carefully. Where the question specifies “MARK ALL THAT APPLY”, you may need to select more than one answer
on the scantron.
1. MARK ALL THAT APPLY: How does neutral cabon-14 differ from neutral oxygen-16? Be sure to consider
each answer carefully. Remember, you can select as many answers as are correct.
a. Oxygen-16 has more protons than carbon-14.
b. Oxygen-16 has more neutrons than carbon-14.
c. Oxygen-16 has more electrons than carbon-14.
d. Oxygen-16 has a larger mass than carbon-14.
e. None of the above.
2. How many electrons are in a carbide anion (C4-)?
a. 2
b. 4
c. 6
d. 10
e. 12
3. Naturally occurring Tungsten (W) consists of the four isotopes below, and has an average atomic mass of
183.85 amu. Using ONLY this information, is it possible to determine which isotope is most abundant in
nature? If so, which one? If this information alone isn’t sufficient to identify the most abundant isotope,
select E.
Tungsten Isotope
Isotopic Mass (amu)
a.)
Tungsten-182
181.948
b.)
Tungsten-183
182.950
c.)
Tungsten-184
183.950
d.)
Tungsten-186
185.954
e.)
Cannot be determined from information provided. Mass spectrometry data would
have to be collected and analyzed.
4. How many significant figures are in this measurement: 0.09010 g?
a. 2
b. 3
c. 4
d. 5
e. 6
5. How would you round the number 3,951 to two significant figures?
a. 3
b. 39
c. 40
d. 4,000
e. 4.0 x 103
6. Using the rule for multiplication & division with significant figures, what is the answer to the calculation
below?
(45.90 g) ÷ (2.70 g/mL) = ________
a. 20 mL
b. 20. mL
c. 17 mL
d. 17.0 mL
e. 17.00 mL
7. Using the rule for addition & subtraction with significant figures, what is the answer to the calculation
below?
(9.71 mL) + (0.592 mL) = _______
a. 10 mL
b. 10.3 mL
c. 10.30 mL
d. 10.302 mL
e. 10.3020 mL
8. Using rules for significant figures, what is the answer to the calculation below?
(10.3 g + 0.19 g) ÷ (19.81 mL) = _________
a. 0.529531 g/mL
b. 0.5295 g/mL
c. 0.530 g/mL
d. 0.53 g/mL
e. 0.5 g/mL
9. Convert this number to PROPER scientific notation: 0.0078 x 107
a. 7.8 x 107
b. 7.8 x 1010
c. 7.8 x 104
d. 7.8 x 109
e. 7.8 x 105
10. Convert this number to standard notation: 13.9 x 10-5
a. 0.00139
b. 0.000139
c. 0.0000139
d. 1390000
e. 13900000
11. Convert 295 ng to g.
a.
b.
c.
d.
e.
2.95 x 109 g
2.95 x 107 g
2.95 x 10-7 g
2.95 x 10-9 g
2.95 x 10-11 g
12. Convert 4.2 x 10-4 mg to µg.
a.
b.
c.
d.
e.
4.2 x 10-13 µg
4.2 x 10-7 µg
4.2 x 10-1 µg
4.2 x 105 µg
4.2 x 1013 µg
13. Convert 8.78 g/cm3 to kg/L.
a.
b.
c.
d.
e.
Hint: 1 cm3 = 1 mL
8.78 x 106 kg/L
8.78 x 103 kg/L
8.78 kg/L
8.78 x 10-3 kg/L
8.78 x 10-6 kg/L
14. Convert 7.74 x 10-8 m3 to cm3.
a.
b.
c.
d.
e.
7.74 x 10-14 cm3
7.74 x 10-11 cm3
7.74 x 10-10 cm3
7.74 x 10-6 cm3
7.74 x 10-2 cm3
15. What is the volume of 28.9 g of gold (Au)?
Information that MIGHT be useful: Gold has a density of 19.3 g/cm3, and a molar mass of 196.96 g/mol.
a.
b.
c.
d.
e.
0.147 cm3
0.668 cm3
1.50 cm3
2.83 cm3
558 cm3
16. How many moles of iron (Fe) are in 3.1 x 1022 atoms of iron?
Information that MIGHT be useful: Iron has a density of 7.870 g/mL, and a molar mass of 55.845 g/mol.
a.
b.
c.
d.
e.
0.051 mol
0.405 mol
2.8 mol
19.4 mol
5.1 x 1044 mol
17. What is the molar mass of Mg(NO3)2 to 3 significant figures?
a. 54.3 g/mol
b. 68.3 g/mol
c. 118 g/mol
d. 134 g/mol
e. 148 g/mol
18. How many moles are in 22.0 g of CO2?
a.
b.
c.
d.
e.
2.00 mol
0.500 mol
0.786 mol
22.0 mol
968 mol
19. How many atoms are present in 32.7 g of Nickel (Ni)?
Information that MIGHT be useful: Nickel has a density of 8.908 g/cm3, and a molar mass of 58.693 g/mol.
a. 3.36 x 1023 atoms
b. 2.98 x 1022 atoms
c. 1.08 x 1024 atoms
d. 9.25 x 1021 atoms
e. 1.97 x 1025 atoms
20. The correct name for Co2S is:
a. cobalt sulfide
b. cobalt sulfate
c. cobalt sulfite
d. cobalt (II) sulfide
e. cobalt (I) sulfide
21. The correct name for Cl3O6 is:
a. trichlorine hexoxide
b. chlorine (IV) oxide
c. chlorine (VI) oxide
d. chlorine (I) oxide
e. dichlorine heptoxide
22. The correct name for FeN is:
a. iron nitrate
b. iron nitride
c. iron nitrite
d. iron (I) nitride
e. iron (III) nitride
23. The formula for iron (II) phosphate is:
a. Fe3P2
b. FePO4
c. Fe2(PO4)3
d. Fe3(PO4)2
e. FePO3
24. MARK ALL THAT APPLY: Which formulas below are INCORRECT with improperly balanced charges? Be
sure to consider each answer carefully. Remember, you can select as many answers as are correct.
a. MgO
b. CaPO4
c. NaClO3
d. NH4SO4
e. AlP
25. MARK ALL THAT APPLY: Which acids below are named incorrectly? Be sure to consider each answer
carefully. Remember, you can select as many answers as are correct.
a. H2SO3 is sulfurous acid
b. H2SO4 is hydrosulfuric acid
c. HCl is hydrochloric acid
d. HNO2 is hydronitric acid
e. HClO3 is chloric acid
26. MARK ALL THAT APPLY: Which substances below are covalent compounds? Be sure to consider each
answer carefully. Remember, you can select as many answers as are correct.
a. NH4OH
b. CS2
c. Na2O
d. P2O5
e. FeCl3
EXTRA CREDIT: Challenge Problem: NO PARTIAL CREDIT--Attempt after finishing the exam and checking your work
1.
(5 points) Verify the following statement:
”There are more atoms within the smallest speck of matter visible to the naked eye, than there are stars in the whole of our Milky
Way galaxy.”
FOR THIS COMPARISON: Determine the total number of atoms in a spherical drop of water with a diameter of 0.05 mm. Compare this
number to the number of stars in our galaxy (approximately 1 x 10 11). Which is larger? By how much?
Hints:
Water has a density of 0.998 g/mL
Volume of a Sphere = 4/3∙π∙r3
diameter = 2 x radius
REFERENCE EQUATIONS:
𝑴𝒂𝒔𝒔
Density = 𝑽𝒐𝒍𝒖𝒎𝒆
Average atomic mass = (isotopic mass)∙(isotopic abundance)
1 mole = 6.022 x 1023 particles
1 cm3 = 1mL
Summing over all isotopes.