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Form Code X NAME________________________________________
CHM 2045, Spring 2015, Exam 3 Review Packet (Broward Teaching Center)
Packet Instructions: Do your best and don’t be anxious. Read the question, re-read the
question, write down all given or valuable information, and write down what you want to
find. As on all graded events, the loving of moles applies.
1. What is the correct molecular geometry of the following, respectively:
ClF4+, COCl2, XeF4, IF3, IO2F2(1) Seesaw, Trigonal Planar, Square Planar, T-Shaped, Seesaw
(2) Tetrahedral, Trigonal Planar, Octahedral, Trigonal bipyramidal, Trigonal
bipyradmidal
(3) Pyramidal, Trigonal planar, planar, Seesaw, T-Shaped
(4) Trigonal Planar, Trigonal pyramidal, Square Planar, T-Shaped, Seesaw
(5) Seesaw, T-shaped, Square planar, Trigonal planar, Trigonal pyramidal
2. What is the standard enthalpy of the reaction per mole of C2H2 ? Is this an endo- or
exothermic process?
2 C2H2 + 5 O2 -> 4 CO2 + 2 H2O
*Bond energies:
C=C: 146 KJ/mol
C-O: 86 KJ/mol C-H: 99 KJ/mol
C=O: 192 KJ/mol
O-H: 110 KJ/ mol
(1) -1009 KJ
(2) +1009 KJ
(3) -472.5 KJ
(4) +504 KJ
(5) -2018 KJ
O=O: 35 KJ/ mol
C-C: 85 KJ/mol
3. Which of the following shows the molecules in order from most polar to least polar?
(1) CH4 > CF2Br2 > CF2H2 > CBr4 > CBr2H2
(2) CF2Br2 > CF2H2 > CBr2H2 > CH4 = CBr4
(3) CF2H2 > CBr2H2 > CF2Br2 > CH4 = CCl4
(4) ClF3 > XeF4 > NBr3 > BF3 > CS2
(5) CH4 > CHCl3 > CHCl2 > CHCl3 > CCl4
4) What is the hybridization of the labeled atoms respectively?
(1) sp, sp2, sp3
(2) sp3, sp3, sp3
(3) sp3, sp2, sp3
(4) The atoms are not hybridized
(5) sp2, sp3d, sd3
5) Which of the following statements about intermolecular forces are false?
(1) C5H12 has a higher boiling point C2H6.
(2) H2O has a larger molar heat of vaporization than Ar.
(3) BiH3 has larger dispersion forces than SbH3
(4) PCl5 has a higher vapor pressure than NH3
(5) All of the above are true
6) Indicate the hybridization change of sulfur during the reaction:
SF4 + 2 H2O -> SO2 + 2 HF
(1) From sp3 to sp2
(2) From sp3d to sp3
(3) From sp4 to sp2
(4) From sp3d2 to sp
(5) sp3d to sp2
7) When silver crystallizes, it forms face centered-cubic cells. The unit cell edge length is
523pm. Calculate the density of silver.
(1)
(2)
(3)
(4)
(5)
5 g/cm3
10g/cm3
6.022*1023 g/cm3
7g/cm3
None of the above
8) Two 1L containers are each at STP. Container A holds He gas and container B holds O2
gas. Which of the following will be false?
(1) Both containers will have the same molarity.
(2) Both containers will have the different density.
(3) Both diatomic gases have the same average velocity.
(4) A has a lower density.
(5) B has a higher density.
9) How many sigma and pi bonds are in one molecule of acetic anhydride? What is the
hybridization of the central oxygen (*)
(1) 12 sigma, 2 pi; sp
(2) 8 sigma, 2 pi, sp3
(3) 12 sigma, 2 pi; sp3
(4) 10 sigma, 4 pi; sp3
(5) 10 sigma, 2 pi; sp
10) A certain liquid has a vapor pressure of 6.91 mmHg at 0 °C. If this liquid has a normal
boiling point of 105 °C, what is the liquid's heat of vaporization in kJ/mol?
(1) +38.4 KJ/mol
(2) -38.4 KJ/mol
(3) -4.111 KJ/mol
(4) + 56.4 KJ/mol
(5) -107.2 KJ/mol
The next two questions 11 and 12 are based on the image below.
11) Which of the following statements is false?
(1) At point A all of the phases are present.
(2) The solid has a higher density than the liquid.
(3) At point B, there is liquid plasma
(4)The temperature corresponding at point E is the normal boiling point.
(5) All of the following statements are true.
12) Which of the following phase changes is occurring from point C to point D?
(1) Evaporation
(2) Sublimation
(3) Melting
(4) Condensation
(5) Deposition
13) A 0.0125 g sample of a gas with an empirical formula of CHF2 is placed in a 165 mL
flask. It has a pressure of 13.7 mmHg at 22.5 °C. What is the molecular formula of the
compound?
(1) CHF2 (2) C2H2F4 (3) C3H3F6 (4) C4H4F8 (5) C5H5F10
14) Which molecule has the strongest intermolecular force?
(1) NH3 - H-Bonding
(2) SO3 - Dipole-Dipole
(3) HBr - H-Bonding
(4) HBr – Dipole-Dipole
(5) NH3 - Dispersion
15) Based on molecular orbital theory, which of the following 2nd-period homonuclear
diatomic species in the most stable?
σ1s < σ*1s < σ2s < σ*2s < π2py = π2pz < σ2px < π*2py = π*2pz < σ*2p
(1) N2
(2) Be2
(3) C2
(4) Li2
(5) B2
16) What is the correct electron configuration for the molecular ion, B2+?
(1) 1s2 *1s2 2s2 *2s2
(2) 1s2 *1s2 2s2 *2s2
(3) 1s2 *1s2 2s2 *2s2
(4) 1s2 *1s2 2s2 *2s2
(5) none of the above.
2p2
2py2
2py2 2pz1
2p1 2py1
17) In a closed 1.00 L flask, 3.5 atm of CO reacts with 4.5 atm of O2 according to the
equation below. Assuming that the temperature remains constant, what is the final
pressure in the flask?
2CO (g) + O2(g) - 2CO2
(1) 1.30 atm (2) 6.25 atm (3) 5.25 atm (4) 7.10 atm (5) 3.14 atm
18) An environmental engineer analyzes a sample of air contaminated with sulfur dioxide.
To a 500. mL sample of air at 750. torr and 38°C, she adds 20.00 mL of 0.01017 M aqueous
iodine, which reacts as follows:
2SO2(g) + I2(aq) + 2H2O(l) → 2HSO41–(aq) + 2I1–(aq) + 4H+(aq)
The excess I2(aq) left over from the above reaction was titrated with 11.37 mL of 0.0105 M
thiosulfate (S2O32–) as follows: I2(aq) + 2S2O32–(aq) → 2I-aq) + S4O62–(aq)
What is the volume % of SO2 in the original air sample?
(1) 1.5% (2) 2.2% (3) 0.55% (4) 0.73 (5) 0.95%
19) The root mean square velocity of a gas molecule is:
I. inversely proportional to its kinetic energy
II. directly proportional to the gas constant R
III. inversely proportional to the square root of its temperature in K
IV. inversely proportional to the square root of its mass
V. directly proportional to the square root of its mass
20) Magnesium metal (0.100 mol) and a volume of aqueous hydrochloric acid that
contains 0.500 mol of HCl are combined and react to completion according to the equation
below. How many liters of hydrogen gas, measured at standard temperature and pressure
(STP), are produced?
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
(1) 2.24 L (2) 4.48 L (3) 5.6 L (4) 11.2 L (5) 22.4 L
21) A 3.0 L flask containing helium at 145 mmHg is connected by a closed valve to a 2.0 L
flask containing argon at 355 mmHg. When the valve is opened and the gases are allowed
to mix equally in the two flasks, what is the total pressure in the two connected flasks after
mixing? (Assume constant temperature)
(1) 230 torr (2) 500 torr (3) 190 torr (4) 434 torr (5) 130 torr
GOOD LUCK and SMILE ON THE EXAM!!!