Download 11/25/15 CHEM 60 Exam 3 Name

11/25/15
ANSWER KEY
CHEM 60 Exam 3
Name: __________________________________
Open-End Questions and Problems
Please read the following. To receive full credit for a question or a problem, in addition to the
correct answer, you must show a neat, complete, and logical method of solution where each
number is labeled with the appropriate unit and the final answer is rounded to the correct
number of significant digits. The correct answer without any work shown will generally get zero
credit! When an explanation is required, it should be brief, but accurate and complete.
There are 7 questions for a total of 42 points. (Exam 3 part with multiple choice questions is
worth 58 points. Both parts combined are 100 points total.
1. (6 points) Fill the blanks in the following table.
Neon
Nitrogen
Ammonia
The number of molecules in 1.00 mole of
none
6.02×1023
6.02×1023
The number of atoms in 1.00 mole of
6.02×1023
1.20×1024
2.41×1024
The number of elements in 1.00 mole of
one
one
two
The number of substances in 1.00 mole of
one
one
one
The number of compounds in 1.00 mole of
none
none
one
The mass in grams of 1.00 mole of
20.18
28.02
17.03
The volume in liters of 1.00 mole of
24.5
24.4
23.3
2. (6 points) Give the chemical formula for each of the following molecules, ions, or formula
units.
H2SO4
sulfuric acid
H2CO3
carbonic acid
HNO2
nitrous acid
HSO4−
hydrogen sulfate ion
HCO3−
hydrogen carbonate
ion
NO2−
nitrite ion
H2SO3
sulfurous acid
CO32−
carbonate ion
N3−
nitride ion
H2S(aq)
hydrosulfuric acid
C4−
carbide ion
NH3
ammonia
Al4C3
aluminum carbide
NH4NO2
ammonium
nitrite
barium hydrogen
Ba(HSO4)2 sulfate
3. (6 points) Write the full-formula, complete ionic, and net ionic equation (FFE, CIE, and
NIE) for each of the two reactions described below. In each equation, indicate physical state
of each reactant and product: (s), (l), (g), or (aq).
(a) Zinc is added to sulfuric acid.
FFE: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
CIE: Zn(s) + 2 H+(aq) + SO42−(aq) → Zn2+(aq) + SO42−(aq) + H2(g)
NIE: Zn(s) + 2 H+(aq) → Zn2+(aq) + H2(g)
(b) Hydrobromic acid is mixed with a sodium carbonate solution.
FFE: 2 HBr(aq) + Na2CO3(aq) → 2 NaBr(aq) + H2O(l) + CO2(g)
CIE: 2H+(aq) + 2Br−(aq) + 2Na+(aq) + CO32−(aq) → 2Na+(aq) + 2Br−(aq) + H2O(l) + CO2(g)
NIE: 2 H+(aq) + CO32−(aq) → H2O(l) + CO2(g)
4. (6 points) Examine the following list of chemical substances to answer questions (a), (b), (c)
and (d).
CH3OH
NH4ClO3
Na2O2
Al2S3
SO3
NH2OH
KMnO4
(a) Which of the substances contain(s) a polyatomic cation?
NH4ClO3
(b) Which of the substances contain(s) a polyatomic anion?
NH4ClO3
Na2O2
KMnO4
(c) Which of the substances contain(s) both ionic and covalent bonds?
NH4ClO3
Na2O2
KMnO4
(d) Which of the substances contain(s) no ionic bonds?
CH3OH
SO3
NH2OH
HClO4
HClO4
5. (6 points) Fill the blanks.
Formula
Name
Al
aluminum atom
Ba2+
barium ion
Br
Electronic
Structure
Number of
Protons per
Molecule,
Atom or Ion
Number of
Number of
Valence
Electrons per
Electrons per
Molecule,
Molecule,
Atom or Ion
Atom or Ion
13
13
3
56
54
0
bromine atom
35
35
7
Br2
bromine
molecule
70
70
14
Br−
bromide ion
35
36
8
CF4
carbon
tetrafluoride
molecule
42
42
32
SO32−
sulfite ion
40
42
26
Ba2+
6. (6 points) What are dispersion forces? How does the strength of dispersion forces relate to
molar mass?
5. (6 points) Fill the blanks.
Formula
Name
Electronic
Structure
Number of
Protons per
Molecule,
Atom or Ion
Number of
Number of
Valence
Electrons per
Electrons per
Molecule,
Molecule,
Atom or Ion
Atom or Ion
aluminum atom
barium ion
bromine atom
Br−
carbon
tetrafluoride
molecule
6. (6 points) What are dipole-dipole forces? How can you tell whether a compound has dipoledipole forces?
5. (6 points) Fill the blanks.
Formula
Name
Electronic
Structure
Number of
Protons per
Molecule,
Atom or Ion
Number of
Number of
Valence
Electrons per
Electrons per
Molecule,
Molecule,
Atom or Ion
Atom or Ion
aluminum atom
barium ion
bromine atom
Br−
carbon
tetrafluoride
molecule
6. (6 points) What is hydrogen bonding? How can you tell whether a compound has hydrogen
bonding?
7. (6 points) Consider the following three molecules:
CO2
(a)
BF3
CH4
In which molecule are the bonds most polar? Explain.
In BF3 molecule. The difference in electronegativity (∆EN) is the largest
between boron and fluorine. The ∆EN’s between carbon and oxygen and
between carbon and hydrogen are smaller.
(b)
Which molecule is the most polar? Explain.
None of the 3 molecules is polar. Each of the 3 molecules is highly
symmetrical with symmetrical distribution of positive and negative charges.
linear
trigonal
planar
tetrahedral