CHEM 2: Midterm Exam 1: Fall 2013
(100 points)
Name: ___________________________________
Please read each question carefully. Be sure to choose the answer with the proper number of significant figures. Where the
question specifies “MARK ALL THAT APPLY”, you may select more than one answer on the scantron.
1.
The vast majority of the VOLUME of a single atom is occupied by the:
a. nucleus
2.
b. electrons
c. protons
d. neutrons
e. It depends on whether it’s a solid, liquid or
gaseous element
The vast majority of the MASS in a single atom is accounted for in the:
a.
nucleus
b. electrons
c. charge
d. It depends on whether it’s a solid, liquid or gaseous element
2-
3.
How many protons are present in the nucleus of a S ion ?
a. 14
b. 16
c. 18
d. 32
e. It depends on the type of sulfur isotope that is being considered.
4.
How many neutrons are present in the nucleus of a S ion?
a. 14
b. 15
c. 16
d. 32
e. It depends on the type of sulfur isotope that is being considered.
5.
How many electrons are in a fluoride anion (F )?
a. 1
b. 8
c. 10
d. 20
e. It depends on the type of fluorine isotope that is being considered.
6.
Which isotope of Chromium (Cr) has the same number of PROTONS as Zinc-65 (Zn with mass number = 65)?
a. Chromium-24
b. Chromium-30
c. Chromium-52
d. Chromium-59
e. None of the above.
7.
Which isotope of Chromium (Cr) has the same number of NEUTRONS as Zinc-65 (Zn with mass number = 65)?
a. Chromium-24
b. Chromium-30
c. Chromium-52
d. Chromium-59
e. None of the above.
8.
Naturally occurring Thallium consists exclusively of the two isotopes below, and has an average atomic mass of
204.38 amu. Select the isotope that is most abundant. Select c. if both are equally abundant, or d. if more
information is needed.
Thallium Isotope
Isotopic Mass (amu)
a.)
Thallium-203
202.9723
b.)
Thallium-205
204.9744
c.)
Neither, they are both equally abundant.
d.)
Cannot be determined from information provided. Mass spectrometry data would have to
be collected and analyzed.
2-
-
9.
How many significant figures are in this number: 0.020080 g ?
a. 2
b. 4
c. 5
d. 6
e. 7
10. Using the rule for multiplication & division, what is the answer to this calculation: (43.997 g) ÷ (13.0 mL) = ?
a. 3.4 g/mL
b. 3.38 g/mL
c. 3.3843 g/mL
d. 3.38438 g/mL
e. None of the above expresses the final answer with the proper number of significant figures.
11. Using the rule for addition & subtraction, what is the answer to this calculation: (1000.3 mL) + (0.979 mL) = ?
3
a. 1.00128 x 10 mL
3
b. 1.0013 x 10 mL
3
c. 1.001 x 10 mL
3
d. 1.00 x 10 mL
e. None of the above expresses the final answer with the proper number of significant figures.
12. Convert this number to proper scientific notation: 0.00007830
5
a. 7.830 x 10
4
b. 7.830 x 10
-4
c. 7.830 x 10
-5
d. 7.830 x 10
e. None of the above are correct.
-9
13. Convert this number to standard notation: 918.7 x 10
a. 0.0000000009187
b. 0.0000009187
c. 9,187,000,000
d. 918,700,000,000
e. None of the above are correct.
14. Convert 439 µg to grams.
Hint: µ = micro = 10
a.
b.
c.
d.
e.
-6
8
4.39 x 10 g
6
4.39 x 10 g
4
4.39 x 10 g
-4
4.39 x 10 g
-6
4.39 x 10 g
15. Convert 75 miles/hr to m/s.
Hint: 1 mile = 1609 meters
a.
b.
c.
d.
e.
8
4.3 x 10 m/s
5
1.2 x 10 m/s
1
3.4 x 10 m/s
2
1.7 x 10 m/s
None of the above
-4
16. Convert 4 x 10 kg to mg.
Hint: k = kilo = 10
a.
b.
c.
d.
e.
3
and m = milli = 10
2
4 x 10 mg
-1
4 x 10 mg
-7
4 x 10 mg
-10
4 x 10 mg
None of the above.
-3
3
3
17. Convert 0.00774 m to mm .
Hint: m = milli = 10
a.
b.
c.
d.
e.
-3
-12
7.74 x 10 mm
-6
3
7.74 x 10 mm
3
7.74 mm
3
3
7.74 x 10 mm
6
3
7.74 x 10 mm
3
3
18. What is the mass of 10.5 cm of iron (Fe)?
Information that MIGHT be useful: Iron has a density of 7.87 g/mL, and an atomic mass of 55.845 amu.
a.
b.
c.
d.
e.
1.47 g
82.6 g
0.750 g
0.188 g
None of the above are correct.
-4
19. How many atoms of Gold (Au) are in 2.70 x 10 moles of Gold?
Information that MIGHT be useful: Gold has a density of 19.3 g/mL, and an atomic mass of 196.96 amu.
a.
b.
c.
d.
e.
19
1.59 x 10 atoms
21
3.14 x 10 atoms
20
1.63 x 10 atoms
22
3.20 x 10 atoms
None of the above are correct.
20. How many grams of CH4 are in 148 moles of CH4?
3
Information that MIGHT be useful: The density of CH4 is 0.66 kg/m . The atomic mass of Carbon (C) is 12.01 amu, while the
atomic mass of Hydrogen (H) is 1.00794 amu.
a.
b.
c.
d.
e.
0
9.22 x 10 grams
3
3.60 x 10 grams
2
2.24 x 10 grams
3
2.37 x 10 grams
None of the above are correct.
6
21. What is the volume of 4.55 x 10 atoms of Nickel (Ni)?
3
Information that MIGHT be useful: Nickel has a density of 8.908 g/cm , and an atomic mass of 58.693 amu.
a.
b.
c.
d.
e.
-15
3
3.95 x 10 cm
-16
3
4.43 x 10 cm
-17
3
4.98 x 10 cm
-18
3
7.55 x 10 cm
None of the above are correct.
22. Magnesium carbide is a:
a. a homogeneous mixture of two different substances, magnesium and carbon.
b. a heterogeneous mixture of two different substances, magnesium and carbon.
c. a single, PURE substance displaying ionic bonding.
d. a single, PURE, molecular covalent substance.
23. Which of the events below are chemical changes (NOT physical changes)? MARK ALL THAT APPLY.
a. ice melting to form liquid water
b. iron metal rusting to form iron (III) oxide
c. liquid water boiling to form steam
d. wood burning to form carbon dioxide
e. None of the above are chemical changes.
24. The correct name for WO3 is:
a. tungsten oxide
b. tungsten trioxide
c. tungsten (III) oxide
d. tungsten (VI) oxide
e. none of the above
25. The correct name for Pb3P4 is:
a. lead phosphide
b. trilead tetraphosphide
c. lead (II) phosphide
d. lead (III) phosphide
e. lead (IV) phosphide
26. The formula for copper (III) sulfite is:
a. Cu3SO3
b. Cu3SO4
c. Cu2S3
d. Cu3(SO3)2
e. Cu2(SO3)3
27. Which of the chemical names below are INCORRECT for the associated formula? MARK ALL THAT APPLY.
a. LiNO3 = lithium nitrite
b. Sr3N2 = strontium nitride
c. Mn(NO2)2 = manganese nitrite
d. iron (III) phosphate = Fe3PO4
28. Choose ALL of the ionic compounds below. MARK ALL THAT APPLY.
a. NO2
b. C6Cl6
c. (NH4)2SO4
d. Ba3P2
e. Fe3(PO4)2
29. Select ALL of the molecular, covalent compounds below. MARK ALL THAT APPLY.
a. C6H12O6
b. P4O10
c. (NH4)2SO3
d. MgO
e. Co3(PO4)2
30. What is the volume of water in the graduated cylinder to the right?
Be sure to report the measurement to the proper number of
significant figures.
a. 40 mL
b. 43 mL
c. 43.0 mL
d. 43.00 mL
e. 43.001 mL
EXTRA CREDIT:
31. (3 points) If the formula for aluminum pyrosilicate is Al2Si2O7, what would be the formula for iron (II) pyrosilicate?
32. (6 points) Verify the following statement: Show work for credit
”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 single spherical grain of sand with a radius of 0.025 mm.
11
Compare this number to the number of stars in our galaxy (approximately 1 x 10 ). Which is larger?
Hints:
Sand is composed of Silicon Dioxide (SiO2) & has an approximate density of 2.65 g/mL
Volume of a Sphere = 4/3∙π∙r
3
REFERENCE EQUATIONS:
Density =
Average atomic mass = (isotopic mass)∙(isotopic abundance)
1 mole = 6.022 x 1023 particles
3
1 cm = 1mL
Summing over all isotopes.