Please sit in Row_____ Seat_____
Name_____PRACTICE_______________________
Chem 105X
Fall 2011
Keller
ABCDEG
Hour Exam 2 Chap 4,5 Kotz
Please:
 Keep this booklet closed until instructed to open it.
 Turn off and remove from your person all electronic items including iPods, cell phones, earbuds,
pagers, computers, programmable and graphing calculators such as TI-84 Plus, 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 9 pages in this exam, including the cover and back sheets.
 The attached back sheet contains reference information including constants and periodic table.
 For questions 21 and 22, 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.
 After you begin, PRINT YOUR NAME at the top of BOTH PAGE 6 and PAGE 7.
Part I. Multiple Choice 4 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. What is the oxidation number of iodine in potassium periodate, KIO4?
a. –1
b. 0
c. +3
d. +5
e. +7
____
2. Which of the following chemical equations show oxidation-reduction reactions?
1. Mg(s) + I2(aq)  MgI2(s)
2. Pb(ClO4)2(aq) + 2 KI(aq)  PbI2(s) + 2 NaClO4(aq)
3. Fe2O3(s) + 3 CO(g)  2 Fe(s) + 3 CO2(g)
a.
b.
c.
d.
e.
1 only
2 only
1 and 2
1 and 3
2 and 3
____
3. Magnesium burns a nitrogen gas atmosphere to produce magnesium nitride. How many moles of Mg will
react with 2.6 moles of N2?
a. 1.3 mol
b. 2.6 mol
c. 3.9 mol
d. 5.2 mol
e. 7.8 mol
____
4. If the complete combustion of an unknown mass of ethylene produces 16 g CO2, what mass of ethylene is
combusted?
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(g)
a. 0.18 g
b. 0.36 g
c. 5.1 g
d. 8.0 g
e. 13 g
1
____
5. The diagram below represents a mixture of oxygen (light) and nitrogen (dark) molecules. If the molecules in
the diagram react to form N2O4 according to the equation
N2 + 2O2  N2O4 , then, respectively, the limiting reactant and the number of N2O4 molecules formed are:
a.
b.
c.
d.
e.
N2 and 1
N2 and 3
O2 and 2
O2 and 3
(none) and 2
____
6. How many moles of Cu2O(s) can be produced when 0.66 mol Cu(s) is combined with 0.40 mol O2(g)? (Write
the balanced chemical equation first.)
a. 0.33 mol
b. 0.40 mol
c. 0.66 mol
d. 0.80 mol
e. 1.06 mol
____
7. Under certain conditions the reaction of ammonia with excess oxygen will produce a 24% yield of NO. What
mass of NH3 must react with excess oxygen to yield 12 g NO?
4 NH3(g) + 5 O2(g)  4 NO(g) + 6 H2O(g)
a. 1.8 g
b. 7.0 g
c. 28 g
d. 50. g
e. 88 g
____
8. In 1.5 M aqueous sulfuric acid, the concentration of hydronium ions H3O+ is...
a. 0.75 moles/L
b. 1.0 moles/L
c. 1.5 moles/L
d. 2.0 moles/L
e. 3.0 moles/L
2
____
9. What is the mass of sodium iodide in 50.0 mL of 2.63  10–2 M NaI(aq)? The atomic weight of Na is 22.99,
and of I is 126.9.
a.
b.
c.
d.
e.
0.00132 g
0.00877 g
0.0788 g
0.197 g
78.8 g
____ 10. What volume of 0.200 M Na2SO4(aq) will completely react with 50.0 mL of 0.135 M Ba(NO3)2(aq)?
Na2SO4(aq) + Ba(NO3)2(aq)  BaSO4(s) + 2 NaNO3(aq)
a. 33.8 mL
b. 67.5 mL
c. 74.1 mL
d. 148 mL
e. 540. mL
____ 11. 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.
____ 12. Specific heat capacity is
a. the quantity of heat needed to change the temperature of 1.00 g of a substance by 1.00 K.
b. the quantity of heat needed to change the temperature of 1.00 g of a substance by 4.184 K.
c. the mass of a substance that 1.00 J of energy will heat by 1.00 K.
d. the temperature change undergone when 1.00 g of a substance absorbs 4.184 J.
e. the maximum amount of heat that 1.00 g of a substance may absorb without decomposing.
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____ 13. Identify the point(s) on the following diagram where the addition of heat will cause some of the sample to
melt.
a.
b.
c.
d.
e.
E, F, and G
A and B
B, C, and D
G and H
B and C
____ 14. 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.
b.
c.
d.
e.
15.5 kJ
16.7 kJ
31.8 kJ
128 kJ
145 kJ
____ 15. 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.
4
____ 16. When H2S(g) reacts with O2(g) according to the following combustion reaction, 518 kJ of energy are evolved
for each mole of H2S(g) that reacts. Complete the following thermochemical equation.
2H2S(g) + 3O2(g)  2H2O(g) + 2SO2(g)
a.
b.
c.
d.
e.
rHo = ?
–518 kJ/mol-rxn
–1036 kJ/mol-rxn
+518 kJ/mol-rxn
+1036 kJ/mol-rxn
+2072 kJ/mol-rxn
____ 17. The thermochemical equation for the combustion of benzene is shown below.
2 C6H6( ) + 15 O2(g)  12 CO2(g) + 6 H 2O(g)
What is the enthalpy change for the combustion of 12.5 g C6H6?
a.
b.
c.
d.
e.
rH = –3909.9 kJ/mol-rxn
–313 kJ
–626 kJ
–1.22  104 kJ
–2.44  104 kJ
–4.89  104 kJ
____ 18. Determine the standard enthalpy change rHo for the reaction:
PbO(s) + Hg(l)  Pb(s) + HgO (s)
given the enthalpies of reaction below.
2 Pb(s) + O2(g)  2 PbO(s)
2 Hg(l) + O2(g)  2 HgO (s)
a.
b.
c.
d.
e.
rH = –434.6 kJ/mol-rxn
rH = –181.6 kJ/mol-rxn
–434.6 kJ/mol-rxn
–181.6 kJ/mol-rxn
+253.0 kJ/mol-rxn
+126.5 kJ/mol-rxn
+616.2 kJ/mol-rxn
____ 19. 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)
5
ABCDEG
Name_____________________________________
Part II. 10 points per question
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 21
Iron reacts with hydrochloric acid.
Fe(s) + 2 HCl(aq) ---> FeCl2 (aq) + H2(g)
What volume of 2.55 M HCl(aq) is required to completely react with, and dissolve, 35.0 g Fe(s)?
6
ABCDEG
Name_____________________________________
Question 22
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.)
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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
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Scratch paper (please detach carefully).
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