CHEM 10: Midterm Exam 2: Fall 2014
(150 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 MIGHT need to
select more than one answer on the scantron.
1.
2.
3.
4.
5.
6.
7.
8.
A blue object would be least likely to absorb which color of light below?
A. Violet
B. Blue
C. Green
D. Yellow
E. Red
MARK ALL THAT APPLY: Which statements below are TRUE?
A. An electronic excitation from a lower energy orbital to a higher energy orbital requires an atom to absorb energy.
B. The amplitude of a wave indicates the distance from one wave peak to the next wave peak.
C. Electromagnetic waves with large wavelengths have high frequencies.
D. Large particles (like baseballs, planets & people) do not behave quantum mechanically because their mass is high and
their wavelength is so small it can be neglected.
E. None of the statements above are TRUE.
How many nodes does the electron orbital to the right have?
A. 1
B. 2
C. 3
D. 4
E. 5
How many CORE electrons does a neutral Phosphorus (P) atom have?
A. 3
B. 8
C. 10
D. 15
E. 18
What is the most likely charge on a Selenium (Se) ion in an ionic compound?
A. +3
B. +2
C. 0
D. -2
E. -3
What is the formula for calcium phosphide?
A. CaP
B. CaP2
C. Ca2P
D. Ca2P3
E. Ca3P2
What is the formula for iron (III) iodide?
A. FeI2
B. FeI3
C. Fe3I
D. Fe3I2
E. Fe2I3
What is the formula for chromium (VI) sulfide?
A. CrS2
B. CrS3
C. Cr4S
D. Cr6S
E. CrS6
9.
10.
11.
12.
13.
14.
What is the formula for dinitrogen pentachloride?
A. N2Cl5
B. N2Cl
C. NCl3
D. NCl
E. None of the above.
What is the name for the molecular, covalent substance: P4O10?
A. phosphorus (IV) oxide (X)
B. tetraphosphorus decoxide
C. diphosphorus pentoxide
D. quadphosphorus oxide
E. None of the above
MARK ALL THAT APPLY: Which statements below are TRUE?
A. Hydrogen can have a maximum of 2 electrons and can NEVER form more than one bond to other atoms.
B. Neon exists as a diatomic molecule (Ne2) so that each neon can share electrons and get to a complete octet.
C. Only the outer most electrons are involved in chemical reactions; the core electrons can essentially be ignored.
D. A triple bond involves the sharing of a total of 3 electrons between two atoms.
E. None of the statements above are TRUE.
How many valence electrons should be included in the Lewis dot structure for the dianion CO32-, which has an overall
charge of -2?
A. 10
B. 12
C. 20
D. 22
E. 24
Hydronium is a cation with the formula H3O+ (overall charge = +1), which is the predominate ion in acidic solutions.
How many valence electrons should be included in the Lewis dot structure for hydronium?
A. 6
B. 7
C. 8
D. 9
E. 10
MARK ALL THAT APPLY: Which Lewis dot structures below are NOT reasonable?
A.
B.
C.
D.
E.
15. Select the most reasonable Lewis dot structure for PCl3.
A.
B.
C.
16. Which bond below is the MOST POLAR?
A. C—O
B. C—Se
C. O—F
D. Se—F
E. S—H
17. MARK ALL THAT APPLY: Which bonds below are NONPOLAR?
A. Se—Br
B. C—N
C. B—H
D. Si—Si
E. N—F
D.
E.
18. Select the best depiction of the bond dipole moment and charge separation present for the polar, covalent N—H bond.
A.
B.
C.
D.
E. None of these: N—H is a NONPOLAR bond.
19. If the reaction below was properly balanced (with the smallest whole number coefficients), what would the coefficient on
the water (H2O) be in the equation below?
___ H3PO4 → ___ H4P2O7 + ___H2O
A.
B.
C.
D.
E.
1
2
3
4
This equation is impossible to balance.
20. If the reaction below was balanced properly (with the smallest whole number coefficients), what would be the
stoichiometric coefficient in front of the diatomic oxygen (O2)?
2 C10H20O + ___ O2 → 20 CO2 + 20 H2O
A.
B.
C.
D.
E.
29
30
39
40
None of the above.
21. If the reaction below was balanced properly with the smallest whole number coefficients, what would be the stoichiometric
coefficient in front of the water (H2O)?
6 H3BO3 → H4B6O11 + ___ H2O
A.
B.
C.
D.
E.
7
8
9
11
This equation is impossible to balance.
22. If the reaction below was balanced properly (with the smallest whole number coefficients), what would be the
stoichiometric coefficient in front of the water (H2O)?
___ P4O10 + ___ H2O → ___ H3PO4
A. 2
B. 4
C. 6
D. 8
E. 10
23. If the reaction below was balanced properly (with the smallest whole number coefficients), what would be the
stoichiometric coefficient in front of the diatomic oxygen (O2)?
___ FeS + ___ O2 → ___ Fe2O3 + ___ SO2
A.
B.
C.
D.
E.
2
4
6
7
8
24. If the reaction below was balanced properly (with the smallest whole number coefficients), what would be the stoichiometric
coefficient in front of the AgNO3?
___ AgNO3 + ___ FeCl3 → ___ Fe(NO3)3 + ___ AgCl
A.
B.
C.
D.
E.
1
2
3
6
9
For questions # 25-29, categorize each reaction as:
A.) Synthesis
B.) Combustion
C.) Decomposition
D.) Single Replacement.
There may be more than one of each category.
25. 3 Fe + 4 H2O → Fe3O4 + 8 H2
26. SO3 + H2O → H2SO4
27. 3 Zn + 2 AlCl3 → 3 ZnCl2 + 2 Al
28. 4 Hg2CrO4 → 2 Cr2O3 + 8 Hg + 5 O2
29. 2 C20H42 + 61 O2 → 40 CO2 + 42 H2O
30. MARK ALL THAT APPLY: Which statements below are TRUE?
A. Gaseous substances have the strongest intermolecular forces of all phases.
B. INTERmolecular forces are the bonds that hold atoms together within molecules.
C. INTRAmolecular forces are the bonds between molecules that keep substances in condensed phases (like liquids
& solids).
D. Stronger dipole-dipole intermolecular forces tend to reduce the melting point of a substance making it easier to
change from a solid to a liquid.
E. None of the statements above are TRUE.
31. Using the Lewis dot structure for PH3 (shown below) & your understanding of VSEPR theory, what is the MOLECULAR
geometry at the central phosphorus atom?
A. trigonal planar
B. trigonal pyramidal
C. tetrahedral
D. bent
E. linear
32. The Lewis dot structure for CH2F2 is provided below. While this structure is written completely flat on the page, the
center carbon actually has a tetrahedral three-dimensional shape. Based on this information, which statement is the
most accurate description of the overall polarity for this molecule?
A. CH2F2 is a NONPOLAR molecule because it only has nonpolar bonds.
B. CH2F2 is a NONPOLAR molecule because the polar C—F bonds point in opposite
directions 180o apart from each other.
C. CH2F2 is a POLAR molecule because of it’s nonplanar shape—the polar C—F bonds
are only 109.5o apart and do NOT point in perfectly opposite directions.
D. CH2F2 is a POLAR molecule because the polar C—F bonds point in opposite directions
180o apart from each other.
E. CH2F2 is an IONIC molecule because of the large difference in electronegativity between hydrogen & fluorine.
33. Assuming all samples are at a constant room temperature, which substance below is most likely to exist as a gas?
A. MgCl2
B. CH3CH3
C. C8H18
D. CH3OH
E. NaCl
34. Assuming all samples are at a constant room temperature, which substance below is most likely to exist as a solid?
A. He
B. CH3CH2CH3
C. CH3F
D. NH3
E. Al2O3
35. Assuming a constant, unchanging volume, what will happen to the pressure of a gas sample as the temperature is
reduced?
A. The pressure of the gas sample should also decrease.
B. The pressure of the gas sample should increase.
C. The pressure will NOT change with a decreasing temperature.
D. Cannot determine from information provided.
36. MARK ALL THAT APPLY: Which statements below are TRUE?
A. On average, the atmospheric pressure at Lake Tahoe (altitude: 6220 feet) should be HIGHER than at sea level.
B. At a constant, unchanging temperature, gasesous argon (Ar) atoms should move faster on average than gaseous
helium (He) atoms.
C. At a constant, unchanging temperature, a balloon should be slightly larger at the top of a mountain than at sea
level.
D. By reducing the volume of a gas, the pressure of a gas will increase. This is how bicycle pumps work.
E. None of the statements above are TRUE.
EXTRA CREDIT: Attempt after finishing the main exam and checking your work
1.
(5 points) Balance the reaction below.
____ S8 + ____ HNO3 → ____ H2SO4 + ____ NO2 + ____ H2O
2.
(5 points) Three different substances have the formula C2H2Cl2 (with two central carbon atoms surrounded by two hydrogen
atoms and two chlorine atoms). Draw the Lewis dot structures for all three substances and predict which substance would
have the LOWEST boiling point. EXPLAIN YOUR REASONING with terminology describing the polarity and intermolecular
forces present in each case.
Periodic Table
Table of Electronegativities