981_4th_Exam_990113
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Which statement is not correct?
A) The equilibrium vapor pressure above a liquid is independent of the volume of liquid present and the volume of vapor present.
B) A volatile liquid has a lower boiling point.
C) The vapor pressure above a liquid increases with temperature.
D) The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external pressure.
E) The stronger the intermolecular forces, the lower the boiling point.
Answer: E
2) A 900 g sample of pure water is shaken with air under a pressure of 0.95 atm at 20 °C. How many milligrams of Ar(g) will be present in the water when solubility equilibrium is reached? Use data from Figure and the fact that the mole fraction of Ar in air is 0.00934.
A) 0.12 mg B) 0.48 mg C) 0.36 mg D) 0.24 mg
Answer: B
3)The measured dipole moment of HCl is 1.07 D. If a H-Cl bond is 127 pm and µ = · d, what is the separated charge in HCl, in coulombs? (1 D = 3.34 × 10-30 C · m)
A) 1.19 × 10-19 B) 119 C) 3.35 × 10-19 D) 2.81 × 10-20 E) 8.43 × 10-3 Answer: D
4) A solution has a 1:3 mole ratio of cyclopentane to cyclohexane. The vapor pressures of the pure compounds at 25°C are 331 mm Hg for cyclopentane and 113 mm Hg for cyclohexane. What is the mole fraction of
cyclopentane in the vapor above the solution?
A) 0.49 B) 0.25 C) 0.66 D) 0.75 E) 0.33
Answer: A
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5) What mass of glucose, C6H12O6, in grams, should be added to 50.0 g H2O to raise the boiling point to 100.45°C? (Kb = 0.512°C m-1)
A) 16.0 B) 50 C) 7.9 D) 0.88 E) 160
Answer: C
6) In which atom is the 2p subshell lowest in energy?
A) Li B) Be C) N D) C E) B
Answer: C
7)Assuming molecular orbital diagrams similar to that of O2, use MO theory to predict the proper ordering of bond energies of the following pairs.
A) N2+ > N2 and O2 > O2+ B) N2 > N2+ and O2 > O2+
C) N2 > N2+ and O2+ > O2 D) N2+ > N2 and O2+ > O2 Answer: C
8) Which of the following molecules would you expect to have the largest dipole moment (µ)?
A)COF2 B)SO3 C) NO D)NOF2 E)CS2
Answer: D
9)Which orbitals overlap in forming the C-C sigma bond of NC-CH3?
A) sp2-sp2 B) sp3-sp3 C) sp-sp D) sp-sp3 E) sp2-sp3
Answer: D
10)The density of a solution that is 20.0% HClO4 is 1.138 g/mL. Calculate the molarity of the HClO4.
A) 1.99 B) 2.26 C) 1.75 D) 0.442 E) 3.45
Answer: B
11)What is the osmotic pressure, in atm, produced by a 20.0% glucose (C6H12O6, FW = 180) solution (d = 1.08 g/mL) separated from pure water at 25°C?
A) 29.3 B) 4.89 C) 25.1 D) 36.0 E) 27.2
Answer: A
12) Copper crystallizes in the cubic close-packed arrangement. The atomic (metallic) radius (labeled r in figure) of a Cu atom is 127.8 pm. Which of the following statement is correct?
A) The length (labeled l in figure) of the unit cell is 361.5 pm B) The volume of that unit cell is 9.3x10-23 cm3
C) The equivalent numbers of atoms in the unit cell is 5 D) The density of metallic copper is 9.835 g/cm3 Answer: A
13) How many of the following processes are endothermic?
freezing vaporization sublimation melting condensation
A) 1 B) 2 C) 3 D) 4 E) 5
Answer: C
14) Which molecular orbital is greatest in energy?
A) * B) * C) D) p E)
Answer: B
15) Which of the following molecules contains polar bonds but is nonpolar?
A)CH2Cl2 B)CCl4 C)H2O D)NH3 E)F2
Answer: B
16)The dipole moment of SO2 is 1.60 D. The shape of SO2 is A) angular.
B) tetrahedral.
C) linear.
D) trigonal planar.
E) impossible to tell.
Answer: A
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17) Which mixture would not be expected to be homogeneous?
A)ethylene glycol, HOCH2CH2OH, and H2O B)KBr and H2O
C)pentanol, CH3(CH2)3CH2OH, and hexane, CH3(CH2)4CH3 D)acetic acid, CH3COOH, and methanol, CH3OH
E)octane, CH3(CH2)6CH3, and heptane, CH3(CH2)5CH3 Answer: C
18) Which of the following would not be angular?
A)OF2 B)ClBr3 C)SO2 D)H2O E)O3
Answer: B
19) Which of the following phase transitions indicates sublimation?
A) solid gas B) liquid solid C) solid liquid D) gas liquid
E) liquid gas Answer: A
20)How much heat, in kJ, is required to melt a 1.55 kg block of ice? ( Hfus = 6.01 kJ/mol)
A) -9.32 B) 518 C) -518 D) 9.32 E) 4.17
Answer: B
21) Which of the following statements about a colloid is not true?
A) A colloid is best described as a dispersion of small particles (1-100 nm in size) in a suitable medium.
B) The particles in a colloid do not settle out with time.
C) An emulsion is a dispersion of liquid particles in a liquid medium.
D) A colloidal mixture is heterogeneous in nature.
E) The Tyndall effect is due to scattering of light by the dissolved particles in the colloid.
Answer: E
22)Consider the phase diagram for CO2. The point on the graph labelled E represents CO2 as a A) liquid.
B) supercritical fluid.
C) solid.
D) gas.
E)CO2 cannot exist at that temperature and pressure.
Answer: B
23)Consider the phase diagram for CO2. In going from phase A to phase B, A)solid CO2 becomes gaseous.
B)gaseous CO2 becomes solid.
C)liquid CO2 becomes gaseous.
D)liquid CO2 becomes solid.
E)solid CO2 becomes liquid.
Answer: A
24)Consider the phase diagram for CO2. Which process is considered as "condensation"?
A) A -> C B) B -> C C) A -> B D) C -> A
Answer: B
25)An aqueous solution of a nonelectrolyte boils at 100.32°C. What is its expected freezing point?
(Kb = 0.512°C m-1, Kf = 1.86°C m-1) A) -1.2
C) -0.83B) 0 D) -0.32
E) Additional information is needed.
Answer: A
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26)Use the VSEPR method to predict the molecular geometry of XeF2.
A)The VSEPR notation is AX2E3 B) The distribution of 22 valence electrons.
C) The Xe and two F atoms lie in a straight line. D) All the describe are correct Answer: D
27) Which of the following hypothetical steps is predicted to be exothermic?
A) pure solvent separated solvent molecules
B) pure solvent and pure solute heterogeneous mixture C) pure solute separated solute molecules
D) separated solvent and solute molecules solution E) not enough information to answer this question Answer: D
28) Which of the following is most likely to involve sp3d2 hybrid orbitals at the central atom?
A) ClF4- B) O3- C)H2O D)N2O E)CF4
Answer: A
29) Which would have the lowest boiling point?
A)OH2 B)CCl4 C)NCl3 D)NH3 E)BF3
Answer: E
30) What is the mole fraction of biphenyl, C12H10, in a solution prepared by dissolving 22.5 g C12H10 (s) in 285 g of benzene, C6H6 (l) ?
A) 0.0384 B) 0.0732 C) 0.414 D) 0.50 E) 0.0789
Answer: A
31) When two atomic orbitals (AO) are combined to form molecular orbitals (MO), which of the following descriptions of the energy of the resulting molecular orbital is most accurate?
A) The MOs are of lower energy than the AO.
B) One MO is higher and one MO is lower than the AO.
C) The MOs are of higher energy than the AO.
D) The MOs are the same energy as the AO.
E) none of these Answer: B
32) When water boils, what primary forces are overcome?
A) Both of the H-O bonds are broken.
B) An H-O bond is broken.
C) The dipole-dipole intermolecular forces are overcome.
D) Hydrogen bonding forces are overcome.
E) Only the dispersion forces are overcome.
Answer: D
33) At 25°C and constant pressure, carbon monoxide gas combines with oxygen gas to give carbon dioxide gas with the evolution of 10.1 kJ per gram of carbon monoxide consumed. What is the value of H for the balanced reaction?
A) 141 kJ/mol B) -283 kJ/mol C) -141 kJ/mol D) 283 kJ/mol E) -566 kJ/mol
34) Which statement is incorrect?
A) For an ideal solution, the H of solution is zero.
B) When 40.0 mL of ethanol and 60.0 mL of water are mixed, the volume of the mixture is 100.0 mL.
C) When ethanol and water are mixed, the solution warms slightly. Therefore, the solution process is exothermic.
D) Ideal solutions form when the intermolecular forces of the solvent and solute are similar.
E) When an ionic compound dissolves in water, the positive and negative ions separate from each other.
Answer: B
35)It is found that 7.24 kJ of heat is required to vaporize 21.5 g of liquid hexane, C6H14. Calculate Hvap of hexane in kJ/mol.
A) 0.879 B) 15.1 C) 75.6 D) 0.333 E) 28.9
Answer: E
36) What is the total number of bonds in the following structure?
A) 1 B) 2 C) 3 D) 4 E) 5
Answer: C
37) The boiling points of the noble gases increase going down the group. What type of intermolecular force best accounts for this fact?
A) hydrogen bonding B) ion-dipole
C) ion-ion
D) London dispersion E) permanent dipole Answer: D
38) How many electrons are there in the 3d orbitals of ground state calcium atom?
A) 0 B) 1 C) 2 D) 5 E) 10
Answer: A
39) Which of the following compounds is predicted to have the highest vapor pressure at STP?
A)CH3OH B)H2O C)C6H12O6 D)CH4 E)C6H5NH2
Answer: D
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40) 50.0 mol H2O(g) (steam) at 100.0 °C and 1.00 atm is added to an insulated cylinder that contains 5.00 mol H2O(s) (ice) at 0 °C. With a minimum of calculation, use the data provided to determine which of the following will describe the final equilibrium condition:Data you will need are Hfusion = 6.01 kJ/mol, Hvapn = 40.6 kJ/mol (at 100 °C), molar heat capacity of H2O(l) = 76 J mol–1 °C–1.
A) liquid water at 50 °C B) steam at 100 °C
C) ice and liquid water at 0 °C D) steam and liquid water at 100 °C Answer: D
41)What will happen if 60.0g KNO3 is added to 100g water at 60°C?
A)All of the KNO3 will dissolve.
B)All of the KNO3 will dissolve, but then it will precipitate.
C)Some of the KNO3 will not dissolve.
D) The solution will become supersaturated.
E)None of the KNO3 will dissolve.
Answer: A
42) Which statement is not true regarding colligative properties?
A) Since the vapor pressure of the solvent is lowered by a nonvolatile solute, the boiling point of the solution is higher.
B) Raoult's Law describes the vapor pressure above a solution.
C) The magnitude depends on whether the solute is an electrolyte or not.
D) The magnitude depends on the identity of the solute.
E) The magnitude depends on the concentration.
Answer: D
43) Which concentration unit varies with temperature?
A) mole fraction B) molarity C) molality D) mass percent
E) All of the above vary with temperature.
Answer: B
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44) Which series correctly identifies the hybridization of the central atom in the following species?
CH2Cl2 CO2 H2CO
A) sp sp sp3 B) sp3 sp sp2 C) sp sp2 sp2 D) sp3 sp2 sp
E) sp2 sp3 sp3 Answer: B
45) For which of the following is hydrogen-bonding not an important intermolecular force?
A)CH3NH2 B)N2 C) HF D)CH3CH2OH E)H2O
Answer: B
46)The hybrid orbitals used by nitrogen in NF3 are
A) sp3d2. B) sp3. C) sp2. D) sp3d. E) sp
Answer: B
47) What mass of NaOH is present in 2.30 L of 5.40 m NaOH aolution (d = 1.15 g/mL)?
A) 516 g B) 216 g C) 470 g D) 497 g E) 571 g
Answer: E
48) According to VSEPR theory, the shape of ICl4- is described as A) tetrahedral.
B) trigonal bipyramidal.
C) square planar.
D) octohedral.
E) square pyramidal.
Answer: C
49) Arrange the following in the expected order of decreasing melting point (highest melting point first, etc.).
KBr MgCl2 MgBr2 NaCl A B C D A) A > B > C > D
B) C > D > A > B C) B > C > D > A D) B > C > A > D E) C > B > D > A Answer: C
50) A 135 g sample of carbon disulfide requires 43.2 kJ of heat to vaporize completely. What is the enthalpy of vaporization for carbon disulfide?
A) 1.77 kJ/mol B) 76.2 kJ/mol C) 24.4 kJ/mol D) 3.13 kJ/mol E) 0.320 kJ/mol
