Please sit in Row_____ Seat_____
Name_____PRACTICE_______________________
Chem 105X
Fall 2009
Keller
ABCDEG
Hour Exam 3 Chap 5, 6, 7 Kotz
Please:
Keep this booklet closed until instructed to open it.
Turn off and remove from your person all electronic items including PDAs, cell phones, earbuds,
pagers, computers, programmable and graphing calculators, and other similar devices.
Place them in your purse or pack on the floor or at the back of the room.
Place all papers, periodic tables, books, coats, packs, on the floor or at the front or back of the room.
All you need are #2 pencils & a non-programmable calculator.
Exam Directions
♣ NOW PRINT YOUR NAME and fill in your STUDENT ID (a number like “309300001” - but not
this number) and the letter of the exam on the bubble sheet.
♣ This is a closed book, 60-minute exam. Use nothing but the materials supplied to answer the
questions.
♣ There are a total of 7 pages in this exam, including the cover and back sheets.
♣ The attached back sheet contains reference information including constants and periodic table.
♣ For questions 17 and 18, show your work, use the correct number of significant figures, and include
proper units in answer and in the work. Write legibly: if your answer cannot be read by the
grader, no credit can be given. USE COMPLETE SENTENCES where requested.
♣ After you begin, PRINT YOUR NAME at the top of BOTH PAGE 5 and PAGE 6.
Part I. Multiple Choice 5 POINTS EACH
Identify the letter of the choice that best completes the statement or answers the question. PUT YOUR ANSWER ON THE
BUBBLE SHEET PROVIDED. Marks in this section of the exam booklet will not be graded.
____
1. A battery-operated power tool, such as a cordless drill, converts
a. electrostatic energy to chemical potential energy.
b. mechanical energy to electrostatic energy.
c. thermal energy to mechanical energy.
d. thermal energy to gravitational energy.
e. chemical potential energy to mechanical energy.
____
2. If 245 J is required to change the temperature of 14.4 g of chromium by 38.0 K, what is the specific heat
capacity of chromium?
a. 0.448 J/g⋅K
b. 2.23 J/g⋅K
c. 4.18 J/g⋅K
d. 4.68 J/g⋅K
e. 92.8 J/g⋅K
____
3. Calculate the energy in the form of heat (in kJ) required to change 50.0 g ice at –15.0 °C to liquid at 65.0 °C.
(Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: ice = 2.06 J/g⋅K, liquid
water = 4.184 J/g⋅K)
a. 15.5 kJ
b. 16.7 kJ
c. 31.8 kJ
d. 128 kJ
e. 145 kJ
____
4. Which of the following statements is CORRECT?
a. If a reaction occurs at constant pressure, w = ∆E.
b. If a reaction occurs at constant pressure, q = ∆H.
c. If a reaction occurs at constant pressure, q = ∆E.
d. If a reaction occurs at constant volume, ∆E > ∆H.
e. If a reaction occurs at constant volume, w = ∆E.
1
____
5. Determine ∆rH for the following reaction,
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)
given the thermochemical equations below.
N2(g) + O2(g) → 2 NO(g)
N2(g) + 3 H2(g) → 2 NH3(g)
2 H2(g) + O2(g) → 2 H2O(g)
a.
b.
c.
d.
e.
∆rH° = +180.8 kJ
∆rH° = –91.8 kJ
∆rH° = –483.6 kJ
–1272.8 kJ
–905.6 kJ
–394.6 kJ
–211.0 kJ
+1272.8 kJ
____
6. Which of the following chemical equations corresponds to the standard molar enthalpy of formation of SO3?
a. SO2(g) + 1/2 O2(g) → SO3(g)
b. 2 SO2(g) + O2(g) → 2 SO3(g)
c. S8(s) + 12 O2(g) → 8 SO3(g)
d. 2 S(s) + 3 O2(g) → 2 SO3(g)
e. 1/8 S8(s) + 3/2 O2(g) → SO3(g)
____
7. When heated in a flame, sodium atoms emit light with a frequency of 5.09 × 1014 s–1. What is the wavelength
of this radiation?
a. 153 nm
b. 170 nm
c. 589 nm
d. 1.70 × 106 nm
e. 1.53 × 1014 nm
____
8. What is the energy (in kJ) of 1.00 mole of photons of green light with a wavelength of 507 nm?
a. 4.24 kJ
b. 60.7 kJ
c. 91.6 kJ
d. 152 kJ
e. 236 kJ
2
____
9. What is the total number of orbitals having n = 5 and = 3?
a. 3
b. 5
c. 7
d. 9
e. 10
____ 10. Which of the following diagrams represent d-orbitals?
a.
b.
c.
d.
e.
1 only
2 only
3 only
4 only
1 and 4
____ 11. Which of the following statements is/are CORRECT?
1. A diamagnetic substance is attracted to a magnetic field.
2. An atom with no unpaired electrons is ferromagnetic.
3. Atoms with one or more unpaired electrons are paramagnetic.
a.
b.
c.
d.
e.
1 only
2 only
3 only
1 and 2
1, 2, and 3
____ 12. How many electrons can be described by the quantum numbers n = 5, = 2, ms = +1/2?
a. 1
b. 3
c. 5
d. 7
e. 9
3
____ 13. Which of the following statements concerning ground state electron configurations is/are CORRECT?
1. For a hydrogen atom with one electron, the 2s and 2p orbitals have identical energies.
2. For a lithium atom with three electrons, the 2s and 2p orbitals have different energies.
3. The effective nuclear charge felt by an electron in a 2p orbital is greater for a carbon
atom than for a boron atom.
a.
b.
c.
d.
e.
1 only
2 only
3 only
2 and 3
1, 2, and 3
____ 14. Which of the following atoms is paramagnetic?
a. Zn
b. Sr
c. Kr
d. Te
e. Ca
____ 15. Which element has the following ground state electron configuration?
a.
b.
c.
d.
e.
Se
As
S
Cl
Ge
____ 16. Which of the following chemical equations refers to the second ionization of Ba?
a. Ba(s) + 2e– → Ba2–(s)
b. Ba+(g) → Ba2+(g) + e–
c. Ba(g) → Ba2+(g) + 2e–
d. Ba(s) → Ba+(s) + e–
e. Ba2+(g) + e– → Ba+(g)
4
ABCDEG
Name_____________________________________
Part II.
For full credit, you must show all conversion factors and the final answer with complete units, use the
correct number of significant figures, and round off correctly. WRITE CLEARLY: if the grader cannot
read your writing, no credit will be assigned.
Question 17
(11 points)
Part A
A 1.994 g sample of ethanol, CH3CH2OH, is combusted in a bomb calorimeter. The temperature of the
calorimeter increases by 10.91°C. If the heat capacity of the bomb is 615.5 J/°C and it contains 1150 g
of water, what is the enthalpy change per mole of ethanol combusted?
(The specific heat capacity of water is 4.184 J/g⋅°C and the molar mass of ethanol is 46.07 g/mol.)
Part B. In several complete sentences, answer the question: “What sequence of events leads to the
increase in the temperature of the calorimeter?” In other words, why basically does the temp of t he
calorimeter increase?
5
ABCDEG
Name_____________________________________
Question 18
(9 points)
Part A
The arrange the following elements in order of increasing atomic radius: krypton, potassium, arsenic,
bromine. Express your answer in a complete sentence.
Part B. Explain why the order of atomic radius is that given above. Please use complete sentences.
6
Avogadro’s number = 6.0221 x 1023 1 in = 2.54000 cm
1 amu = 1.661 x 10-24 g
1 mile = 5280.0 ft
7