CHEM 1A: FINAL EXAM--Spring 2014 Name:_____________________________
PLEASE READ EACH QUESTION CAREFULLY. All multiple choice questions have 1 answer unless
otherwise specified. ONLY where the question specifies “MARK ALL THAT APPLY,” may it be
necessary to mark more than one answer on the Scantron. You may need to consult the
reference equations, constants and data tables in the back of the exam for pertinent
information.
MULTIPLE CHOICE QUESTIONS:
1. Which isotope would have the same number of PROTONS as phosphorus-31?
A. Sulfur-32
B. Aluminum-31
C. Silicon-30
D. Phosphorus-30
E. None of the above.
2. MARK ALL THAT APPLY: In theory, which atoms or ions would have the same total number of electrons
as a sulfur dication, S2+?
A. P+
B. Si
C. Ar
D. ClE. None of the above.
3. Which isotope below would be LEAST stable & MOST LIKELY to undergo β+ decay?
A. Neon-20
B. Helium-4
C. Sulfur-32
D. Carbon-9
E. Magnesium-24
4. Identify the WEAKEST bond below.
A. Sb—Sb
B. As—As
C. Sb—Cl
D. As—Cl
E. Cannot determine from information provided.
5. Rank the bonds below from SHORTEST to LONGEST: (short < long)
A. Si—C < P—C < P—N < P—O < P=O
B. Si—C < P—C < P—N < P=O < P—O
C. P—N < P=O < P—O < Si—C < P—C
D. P=O < P—O < P—N < Si—C < P—C
E. P=O < P—O < P—N < P—C < Si—C
6. Rank the compounds below from LOWEST boiling point to HIGHEST boiling point: (low < high)
A. CH3OH < N2 < O2 < MgS < NaCl
B. CH3OH < N2 < O2 < NaCl < MgS
C. N2 < O2 < CH3OH < MgS < NaCl
D. O2 < N2 < CH3OH < NaCl < MgS
E. N2 < O2 < CH3OH < NaCl < MgS
7. Which compound below has the HIGHEST vapor pressure at 25 oC?
A. Br2
B. CBr4
C. I2
D. Hg
E. Hg2Br2
8. Assuming a constant pressure for all samples, which gas has the HIGHEST density?
A. SF6(g) at 25 oC
B. CO2(g) at 25 oC
C. CH3CH2CH2CH3(g) at 25 oC
D. CH3CH2CH2CH3(g) at 50 oC
E. CH4(g) at 100 oC
9. Consider the gas phase reaction below occurring inside a vessel with a constant volume:
CH4(g) + 2 O2(g) → CO2 + 2 H2O(g)
ΔHo = -802 kJ
If the heat of the reaction is not absorbed by the surroundings but stays contained in the vessel, how
would the pressure change within the container?
A. The pressure would INCREASE.
B. The pressure would DECREASE.
C. The pressure would NOT CHANGE overall.
D. Cannot determine from information provided.
10. Which compound below would be the LEAST water soluble?
A. SO2
B. CH3CH2CH2OH
C. Au
D. Mg(NO3)2
E. H2SO4
11. Consider an aqueous solution of lead (II) chloride with a concentration of 270.0 ppm. If 5.00 mL of this
solution is diluted to a final volume of 10.0 L, what is the final concentration of PbCl2 (in ppm)?
A. 135 ppm
B. 90.0 ppm
C. 13.5 ppm
D. 9.00 ppm
E. 0.135 ppm
12. Which electron transition below would ABSORB the SHORTEST wavelength of light? (where ni is the
initial state and nf is the final state)
A. ni = 1 → nf = 20
B. ni = 1 → nf = 2
C. ni = 2 → nf = 18
D. ni = 18 → nf = 20
E. ni = 20 → nf = 5
13. MARK ALL THAT APPLY: Which Lewis dot structures below are INCORRECT?
A.
B.
C.
D.
E.
14. Given the Lewis dot structure below in combination with VSEPR Theory, determine the MOLECULAR
shape of the central iodine atom in iodine trichloride.
A. T-shaped
B. Trigonal planar
C. Trigonal pyramidal
D. Trigonal bipyramidal
E. Octahedral
15. Consider the reaction of borane (BH3) with ammonia (NH3) shown below:
BH3 +
How would the bond angles change as the reactants are convert to the product?
A.
B.
C.
D.
E.
The H—B—H angle would INCREASE & the H—N—H bond would INCREASE.
The H—B—H angle would DECREASE & the H—N—H bond would INCREASE.
The H—B—H angle would INCREASE & the H—N—H bond would DECREASE.
The H—B—H angle would DECREASE & the H—N—H bond would DECREASE.
The bond angles would NOT CHANGE over the course of the reaction.
16. The formula for lead (IV) zirconate is Pb(ZrO3)2. Based on this information, what is the formula for
ammonium zirconate?
A. NO2ZrO3
B. NH4ZrO3
C. (NH4)4ZrO3
D. (NH4)2ZrO3
E. None of the above
17. Identify the reducing agent in the reaction below:
3 Mg(NO3)2(aq) + 2 (NH4)3PO4(aq) → Mg3(PO4)2(s) + 6 NH4NO3(aq)
2+
A. Mg (aq)
B. NO3-(aq)
C. NH4+(aq)
D. PO43-(aq)
E. None of the above: this is NOT a redox reaction.
18. Identify the component that is REDUCED in the reaction below:
CS2 + 3 Cl2 → CCl4 + S2Cl2
A. CS2
B. Cl2
C. CCl4
D. S2Cl2
E. None of the above: this is NOT a redox reaction.
19. In the operation of a refrigerator, which step is EXOTHERMIC, releasing heat outside of the
refrigerator?
A. Adiabatic compression
B. Isothermal compression
C. Adiabatic expansion
D. Isothermal expansion
E. None of above: a refrigerator does not release heat.
20. What is the proper form of iodine in its standard state at 25 oC?
A. I(g)
B. I-(aq)
C. I2(g)
D. I2(l)
E. I2(s)
21. Consider the ENDOTHERMIC reaction below:
Based ONLY on the information above, what can be said about the relative bond strengths in the
reactants and products?
A.
B.
C.
D.
E.
a C=O double bond must be MORE THAN twice as strong as a C—O single bond.
a C=O double bond must be LESS THAN twice as strong as a C—O single bond.
a C=O double bond must be MORE THAN twice as strong as a C—H single bond.
a C=O double bond must be LESS THAN twice as strong as a C—H single bond.
NONE of these conclusions can be reached from the information provided above.
22. Consider the reaction below where nitrogen dioxide forms from the corresponding ATOMS:
2 O(g) + N(g)  NO2(g)
ΔHo = ?
MARK ALL THAT APPLY: What can be said about the change in enthalpy for this reaction?
A.
B.
C.
D.
E.
This reaction would be ENDOTHERMIC.
This reaction would be THERMONEUTRAL.
This reaction would be EXOTHERMIC.
ΔHo = +33.2 kJ/mol
ΔHo = -938 kJ/mol
23. If 154 mol of oxygen gas fully reacts in the combustion below, how many moles of CO2 gas will be
produced?
2 C4H10(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(ℓ)
A. 1256 mol
B. 616 mol
C. 250. mol
D. 94.8 mol
E. 38.5 mol
FREE RESPONSE QUESTIONS: Please read each question carefully. Report all final answers in PROPER
scientific notation with the correct number of significant figures. SHOW YOUR WORK FOR PARTIAL CREDIT.
1. Fill in the table below. Where the formula has been provided, give the systematic name. Where the
name has been given, write the corresponding formula.
Formula
Systematic Name
MoO3
Aluminum perchlorate
Zr(SO3)2
Hypochlorous acid
H3PO3
Tetraphosphorus heptasulfide
2. A. Aluminum-26 is used to determine the terrestrial age of meteorites. Write the balanced reaction for
positron emission (β+ decay) from Al-26.
B. Static eliminators use polonium-210 as an alpha emitter to ionize air, thereby allowing static cling to
more rapidly dissipate. Write the balance reaction for the alpha decay of Po-210.
3. Draw a 7p atomic orbital. Label & distinguish between all RADIAL & ANGULAR nodes.
4. A chlorine-chlorine single bond has a bond energy of 243 kJ/mol. What is the MINIMUM frequency of
light (in Hz) required to break a single Cl—Cl bond. Assume breaking one bond requires one photon.
5. It takes 8.020 x 10-19 J of energy to eject a single electron from the surface of a metal. How many
electrons can be ejected if 9.820 x 1012 photons, each with an energy of 1.150 x 10-18 J, are shone onto
the surface of this metal? Explain your reasoning with one sentence.
6. A. Draw the lowest energy Lewis dot structure for ozone, O3. Include ALL resonance structures.
Hint: The molecule is acyclic (not in the shape of a ring); it has one central oxygen with two outer
oxygen atoms.
B. Calculate & label the FORMAL CHARGE on each oxygen in the Lewis dot structures above.
C. Based on the Lewis dot structure from part A. above, what is the ELECTRON geometry about the
central oxygen in ozone?
7. A typical automobile tire is inflated to a pressure of 30.0 psi. Assume that the tire was inflated when
the air temperature was 20.3 oC. If the car is then driven at high speeds, which increases the
temperature of the tire to 43.8 oC, what is the new pressure in the tire? Assume a constant tire volume.
8. A. At a laboratory party, a helium-filled balloon with a volume of 2.00 L at 22 oC was placed into a large
container of liquid nitrogen (T = -196 oC). Assuming a constant pressure of 1.00 atm, calculate the final
volume of the balloon (VHe) after it has cooled to liquid nitrogen temperatures.
B. If the balloon was instead filled with oxygen gas, which deviates from ideal gas behavior at liquid
nitrogen temperatures, how would the final volume (VO2) compare to the final volume of the helium
balloon (VHe) from part A. above. Explain your reasoning.
9. Engineers will sometimes express specific heat capacities in British thermal units per pound per degree
Celsius (Btu/lb·oC). Perform the conversion below using dimensional analysis and any of the conversion
factors provided. Report the final answer in PROPER SCIENTIFIC NOTATION.
Specific Het Capacity of Iron (Fe):
0.19
𝐵𝑡𝑢
𝑙𝑏·℃
→ _____________________
𝑛𝐽
µ𝑔·℃
4.184 J = 1 calorie
1 Btu = 1.0545 kJ
1 L·atm = 101.325 J
1 kg = 2.204 lb.
1 mol Fe = 55.85 g Fe
1.00 cm3 = 7.87 g Fe
10. Some solar energy devices used in homes circulate air over a bed of rocks that absorbs thermal energy
from the sun. If a house uses a solar heating system that contains 2500 kg of sandstone rocks, what
amount of energy is stored as heat (in kWh) if the temperature of the rocks increases from 20.0 oC to
34.5 oC? Hint: Sandstone has a specific heat capacity of 0.220 cal/g·oC & 1 kWh = 3600 kJ.
11. For each reaction below, label the change in enthalpy as POSITIVE (+), NEGATIVE (-) or ZERO (0).
A. NaCl(s) → Na+(g) + Cl-(g)
ΔH = _________
B. H2(g) + Cl2(g) → 2 HCl(g)
ΔH = _________
C. F(g) + 1 e- → F-(g)
ΔH = _________
D. O-(g) + 1 e- → O2-(g)
ΔH = _________
E. 6 CO2(g) + 6 H2O(l) → C6H12O6(s) + 6 O2(g)
ΔH = _________
F. Na+(g) + 1 e- → Na(g)
ΔH = _________
12. A. Write the balanced reaction for the formation of solid calcium phosphate from its corresponding
elements in their standard states.
B. Determine the change in enthalpy for the reaction as you’ve written it in part A. above.
13. Consider the dissolution of solid potassium chloride in water:
KCl(s)  K+(aq) + Cl-(aq)
ΔHodissolution = +18.04 kJ/mol
If 10.531 grams of KCl(s) is dissolved in 100.0 mL of water at 22.2 oC, what would be the final temperature of
the water at thermal equilibrium? Assume only the water absorbs OR releases the heat associated with the
dissolving process.
14. Consider the four endothermic reactions below:
Reaction 1: H2O(s)  2 H(g) + O(g)
Reaction 2: H2O(s)  H2O(g)
Reaction 3: Al2O3(s)  2 Al3+(g) + 3 O2-(g)
Reaction 4: CO2(s)  CO2(g)
A. Rank these reactions from LEAST endothermic to MOST endothermic:
LEAST Endothermic: _____________<_____________<_____________<_____________: MOST Endothermic
B. Explain your reasoning for part A. Use terms & concepts from the theories of bonding we have learned.
15. Calculate the change in enthalpy (ΔHo) for the reaction below.
B2O3(s) + 3 COCl2(g) → 2 BCl3(g) + 3 CO2(g)
ΔHo = ______________
16. Use Hess’s law to calculate the change in enthalpy for the reaction below:
CS2(l) + 6 H2O2(l) → CO2(g) + 6 H2O(l) + 2 SO2(g)
Relevant Information:
CO2(g) + 2 SO2(g) → CS2(l) + 3 O2(g)
ΔHo = +1077 kJ
H2(g) + O2(g) → H2O2(l)
ΔHo = -188 kJ
2 H2(g) + O2(g) → H2O(l)
ΔHo = -572 kJ
ΔHooverall = _______________
17. Consider the combustion of white phosphorus (P4(s)) to yield tetraphosphorus decoxide as depicted
below using Lewis dot structures:
+ 5 O=O
ΔHoreaction = -2984.0 kJ
(Lone pair electrons excluded for clarity)
Based on this information and the reference tables provided at the end of the exam, calculate the
approximate bond energy of a P=O DOUBLE bond (in kJ/mol).
18. Write the balanced NEURALIZATION reaction between aqueous sulfurous acid and aqueous calcium
hydroxide.
19. Write the balanced COMBUSTION reaction for stearic acid, CH3(CH2)16CO2H.
20. Write the balanced SYNTHESIS reaction to make diphosphorous pentasulfide from P 4 and S8.
21. To form the precipitate PbCl2(s) (278.1 g/mol), 2.88 g of NaCl (58.44 g/mol) and 7.21 g of Pb(NO3)2
(331.19 g/mol) were mixed in 500 mL of water. What is the maximum amount of precipitate that could
form from this mixture (in grams)?
22. Consider the reaction of iron metal with chromate ions to produce iron (III) oxide and chromium (III)
oxide.
A. Start by balancing the half reactions:
 Balanced REDUCTION half reaction:
 Balanced OXIDATION half reaction:
B. Next, balance the overall reaction in ACIDIC conditions:
C. Finally, balance the overall reaction in BASIC conditions:
23. For each set of reactants below predict the possible products AND balance the equation.
A. ______ Mg(s) + ______FeCl3(aq) → _______________________________________________
B. ______ H2(g) + ______AuCl(aq) → _______________________________________________
C. FOR EACH REACTION ABOVE: if the reaction is NOT expected to occur, CIRCLE THE REACTANTS. If
the reaction IS expected to occur, CIRCLE THE PRODUCTS.
24. The compound para-nitrophenol (molar mass = 139 g/mol) reacts with sodium hydroxide in
aqueous solution to generate a yellow anion via the reaction shown below:
Because the amount of para-nitrophenol is easily estimated from the intensity of the yellow color that
results when excess NaOH is added, reactions that produce para-nitrophenol are commonly used to
measure the activity of enzymes, the catalysts in biological systems. What volume of 0.105 M NaOH
solution must be added to 50.0 mL of a solution containing 7.20 × 10−4 g of para-nitrophenol to ensure
that formation of the yellow anion is complete?
EXTRA CREDIT: Only attempt this challenge problem if you’ve finished and checked the rest of your exam.
Explain the mechanics behind the demonstration presented in class on the thermodynamic drinking bird.
The drinking bird is a type of heat engine: a mechanical device that extracts work from a temperature
differential. In your explanation of the device mechanics, you must address (1) the source of the energy that
drives this device, (2) why the temperature differential exists, and (2) the effect this difference in temperature
has on the operation of the device. Use terms from thermodynamics, thermochemistry, intermolecular forces,
and be specific regarding the gas laws that compel the bird to continue to drink. Be thorough but precise in
your language.
Hint: The glass of water is critical to the operation of this engine, and the liquid inside the bird is methylene
chloride (CH2Cl2 which has a boiling point of 39.6 oC).
REFERENCE EQUATIONS & CONSTANTS:
1 mol = 22.4 L at STP
R = 0.08206 L·atm/mol·K = 62.37 L·mmHg/mol·K = 8.314 J/mol·K
1.00 atm = 760 mmHg = 101.3 kPa = 14.7 psi
Kelvin = oC + 273.15
oC
PV = nRT
=5/9·(oF - 32)
Molarity = moles of solution/Volume of solution (L)
M 1V 1 = M 2V 2
𝑵𝑨 = 6.022141 𝑥 1023
𝒄 = 𝝀𝝂
where 𝑐 = 2.9979 𝑥 108 𝑚 ∙ 𝑠 −1
𝜆𝐷𝑒 𝐵𝑟𝑜𝑔𝑙𝑖𝑒 =
ℎ
𝑚∙v
1
𝜆𝑝ℎ𝑜𝑡𝑜𝑛
𝑬 = ℎ𝜐
= 𝑅𝐻 (
𝐸𝑝ℎ𝑜𝑡𝑜𝑛 = Φ + 𝐾𝐸 where Φ = work function
1
2
𝑛𝑓
−
1
𝑛𝑖2
)
where ℎ = 6.626 𝑥 10−34 𝐽 ∙ 𝑠
where 𝑅𝐻 = 1.097 𝑥 10−2 𝑛𝑚−1
1
𝐾𝐸 = 2 𝑚 ∙ v2 where 𝑚𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 = 9.109 𝑥 10−31 𝑘𝑔
q = mCpΔT where ΔT = (Tfinal – Tinital)
Cp,H2O(l) = 4.184 J/g·oC