1413.001 CHEM - Exam 3 November 2, 2011 - Part 1
Molar Masses: C6H14 - 86.
H2O - 18.
C2H4 - 28.
H2 - 2.
Li - 6.9
NH4Cl - 53.5
CH3OH - 32.
C2H6 - 30.
CHEM 1413.001 - Exam 3 November 2, 2011 - Part 1
Name______________________________
(27)
MULTIPLE CHOICE (Circle the ONE correct answer)
NOTE: Required Molar Masses and non-metric conversion factors are
given on the cover sheet.
1. Which of the following statements is/are true.
(i)
(ii)
(iii)
(A)
Enthalpy is defined by: H = E + PV
q = H for constant volume reactions
Hesss law is valid becauses work (w) is a state function
i only
(B) ii only
(C) i and iii
(D) None
2. The Enthalpy of Fusion of hexane, C6H14, is 12.4 kJ/mol, and the constant
pressure molar heat capacity is 190 J/mol-oC. What is the heat involved in
cooling 129 grams of liquid hexane from 25 oC to its melting point, -95 oC, and
freezing the sample?
(A) -34.2 kJ
(B) -38.6 kJ
(C) -15.6 kJ
(D) -52.8 kJ
For #3 - #4: Consider the thermochemical equation for the decomposition of ethene:
2 C2H4(g) 4 C(graphite) + 4 H2(g)
H = -104 kJ
3. The heat involved in the production of 42 grams of ethene from the elements
carbon and hydrogen, is
(A) +156 kJ
(B) +78 kJ
(C) -78 kJ
(D) -208 kJ
4. If ethene is reacted, and 520 kJ of heat is released, how many grams of H2 have
been formed?
(A) 10 g
(B) 1.25. g
(C) 40. g
(D) 20. g
For #5 - #6: Consider the reaction of Lithium with water:
2 Li(s) + 2 H2O(l) 2 LiOH(aq) + H2(g)
Ho = -160 kJ
The Enthalpy of Fusion of H2O(s) is 6.0 kJ/mol and the specific heat capacity of
H2O(l) is 4.18 J/g-oC.
5. When 10 grams of Li(s) is dropped in a container containing ice and liquid water
at 0 oC, approximately how many grams of ice will melt?
(A) 78.5 g
(B) 350 g
(C) 19.3 g
(D) 700 g
6. When 10 grams of Li(s) is dropped into 900 grams of H2O(l), originally at 23 oC,
what will be the approximate final temperature of the water?
(A) 62 oC
(B) 85 oC
(C) 54 oC
(D) 31 oC
7. H for the combustion (reaction with O2) of 2 (two) moles of propane, C3H8, to
form CO2 and H2O is -4446. kJ. From this information and the enthalpies of
formation of CO2 (-394 kJ/mol), and H2O (-286 kJ/mol), what is the Enthalpy of
Formation of propane?
(A) +103 kJ/mol
(B) -206 kJ/mol
(C) -103 kJ/mol
(D) There is insufficient data given to perform this calculation
8. When 8. grams of NH4Cl(s) is dissolved in water, the water cools down and the
NH4Cl absorbs 5.6 kJ of heat. What is H for dissolving 1 mol of NH4Cl in water?
(A) +37.5 kJ
(B) +44.8 kJ
(C) -37.5 kJ
(D) The specific heat capacity, Cs, and mass, m, of water is required.
9. The Fuel Value of methanol, CH3OH, is 23 kJ/g. Therefore, H for combusting
3 (three) moles of methanol in O2 is approximately:
(A) -100 kJ
(B) -2200 kJ
(C) -740 kJ
(D) +2200 kJ
-------------------------------------------------------------------------------------------------------------------------Two problems on following pages.
PROBLEMS (You MUST show your work to receive credit)
(10) 1.
A 120 g sample of ethane gas, C2H6(g), is initially at 250 oC in a 200. Liter container
(the pressure in the container is 0.86 atm.). The sample is cooled at constant
volume to 50 oC (and the pressure decreases to 0.53 atm). The constant volume
molar heat capacity of ethane is 44.6 J/mol-oC.
Calculate q, w and E for this process, all in kJ (kJoules).
(10) 2.
From the following of enthalpies reaction:
2 B2O3(s) 4 B(s) + 3 O2(g)
H = +2510 kJ
4 H2(g) + 2 O2(g) 4 H2O(l)
H = -1144 kJ
B2O3(s) + 3 H2O(l) B2H6(g) + 3 O2(g)
H = +2148 kJ
Calculate the enthalpy change for the reaction,
B2H6(g) 2 B(s) + 3 H2(g)
CHEM 1413.001 - Exam 3 November 2, 2011 - Part 2
Constants: NA = 6.02x1023 mol-1
h = 6.63x10-34 J-s
Conversion Factors: 1 eV = 1.60x10-19 J
Molar Masses:
NaCl - 58.5
c = 3.00x108 m/s
1 hr = 3600 s
Ca3(PO4)2 - 310.3
CHEM 1413.001 - Exam 3 November 2, 2011 - Part 2
Name______________________________
(39)
MULTIPLE CHOICE (Circle the ONE correct answer)
NOTE: Required Molar Masses and non-metric conversion factors are
given on the cover sheet.
10. A stellar object is emitting photons with a frequency of 2.5x1014 s-1. If a detector
is capturing 5x108 photons/s, what is the total energy of the photons detected in
one hour?
(A) 3.0x10-7 J
(B) 2.2x106 J
(C) 140 J
(D) 1.4x10-18 J
11. Which of the following sets of quantum numbers are allowed for an electron in a
hydrogen atom?
(i) n = 4, l = 3, ml = -2, ms = -
(ii) n = 3, l = -1, ml = 0, ms = +
(iii) n = 5, l = 1, ml = -1, ms = -
(A) i & ii
(B) ii & iii
(C) i & iii
(D) i, ii & iii
12. How many orbitals are contained in the n = 4 shell of an atom?
(A) 9
(B) 16
(C) 18
(D) 32
13. What is the energy of a photon with a wavelength of 6500. nm?
(A) 3.1x10-20 J
(B) 3.1x10-29 J
(C) 1.0x10-28 J
(D) 4.6x1013 J
14. Of the four atoms, K, Ca, As and Se, ___ has the most unpaired electrons and
____ has the least unpaired electrons.
(A) Se , K
(B) As , Ca
(C) Se , Ca
(D) As , K
15. The complete electron configuration of the Co3+ ion is:
(A) 1s22s22p63s23p64s23d7
(B) 1s22s22p63s23p64s23d4
(C) 1s22s22p63s23p63d6
(D) 1s22s22p63s23p64s23d10
16. Arrange the following atoms in order of increasing atomic radius:
Pb , Br , Te , Sb
(A) Te < Br < Sb < Pb
(B) Br < Te < Pb < Sb
(C) Pb < Sb < Te < Br
(D) Br < Te < Sb < Pb
17. Of the four atoms, As, Cl, Br, Ga, ____ has the largest radius and ____ has the
largest First Ionization Energy.
(A) Cl , As
(B) Be , Ga
(C) Cl , Ga
(D) Ga , Cl
18. The Electron Affinity of an atom is defined as the energy change for which one of
the following processes?
+
-
+
(A) M M + e
-
(B) X X + e
-
-
(C) X + e X-
(D) X+ + e X
19. Which of the following atoms would have a fourth ionization energy much larger
than its third ionization energy?
(A) Mg
(B) Al
(C) Si
(D) P
20. The total number of lone pairs of electrons in the PO-1 ion is/are:
(A) 4
(B) 3
(C) 2
(D) 1
21. The number of lone pairs of electrons around the central atom in TeBr2 is:
(A) 0
(B) 1
(C) 2
(D) 3
22. In the AsS-1 ion (As=Arsenic), the Arsenic-Sulfur bond is a ____ bond and there
is/are _____ lone pairs of electrons around the Sulfur atom.
(A) double, 1
(B) double , 2
(C) triple , 1
(D) triple , 2
_________________________________________________________________________
TWO PROBLEMS (You MUST show your work to receive credit)
(05) 3.
Write both the Complete and Condensed electron configuration of Astatine (At).
(09) 4.
When photons of light with a wavelength of 140 nm strike a platinum (Pt) electrode,
the ejected electrons have a kinetic energy of 5.2x10-19 J. Calculate the Binding
Energy of an electron in platinum, in eV (electron-volts).