AP Chemistry AP Chemistry Name by chenmeixiu


									AP Chemistry                                                           Name ________________________
Fall Semester Practice Multiple Choice                                                   Period _____
Multiple Choice: Briefly show/explain why the multiple choice answer is correct in the space provided (no calculator).
1. Copper has two naturally occurring isotopes, Cu and         Questions 6-8
    65                                65
       Cu. What is the abundance of Cu if the average atomic      (A) Heisenberg uncertainty principle
    mass of copper is 63.5?                                       (B) Pauli exclusion principle
    (A) 90%       (B) 70%      (C) 50%        (D) 25%             (C) Hund's rule (principle of maximum multiplicity)
                                                                  (D) Shielding effect
                                                               6. Can be used to predict that a gaseous carbon atom in its
                                                                  ground state is paramagnetic.
2. Which of the following particles is emitted by an atom of
    39                                          39
       Ca when it decays to produce an atom of K?
                               (C)           (D) 
         1             1              -             +
    (A) 0n        (B) 1H
                                                               7. Indicates that an atomic orbital can hold no more than two

3.   After 195 days, a 10.0 g sample of pure Zr has decayed
     to the extent that only 1.25 g of the original Zr remains.
     The half-life of Zr is closest to                            8.   Predicts that it is impossible to determine simultaneously
     (A) 195 days                 (B) 98 days                          the exact position and the exact velocity of an electron.
     (C) 65 days                  (D) 49 days

                                                                  9.   Which set of quantum numbers (n, l, ml, ms) best describes
Questions 4-5 The diagram shows the energy levels (in eV) for          the valence electron of highest energy in a ground-state
hydrogen gas.                                                          gallium atom (Z = 31)?
                                                                       (A) 4,0,0,½ (B) 4,0,1,½ (C) 4,1,1,½ (D) 4,1,2,½

                                                                  Questions 10-12 refer to neutral atoms for which the atomic
                                                                  orbitals are represented below.
                                                                       (A) 1s()
                                                                       (B) 1s() 2s() 2p()()( )
                                                                       (C) 1s() 2s() 2p()()()
                                                                       (D) [Ar] 4s() 3d()()()()()
                                                                  10. Is in an excited state

                                                                  11. Has exactly five valence electrons

                                                                  12. Has the highest first ionization energy

4.   What is the energy, in eV, of a photon emitted by an         13. The first seven ionization energies of element X are shown
     electron as it moves from the n = 6 to the n = 2 energy          in the table below.
     level in a hydrogen atom.                                                         Ionization Energy (kJ•mol )
     (A) 0.38 eV (B) 3.02 eV (C) 3.40 eV (D) 13.60 eV                   1st      2nd      3rd       4th     5th     6th      7th
                                                                       787      1,580 3,200 4,400 16,000 20,000 24,000
                                                                      On the basis of these data, element X is most likely a
                                                                      member of which of the following groups of elements?
5.   A photon having energy of 9.4 eV strikes a hydrogen atom         (A) Alkaline earth metals (B) Boron group
     in the ground state. Why is the photon not absorbed by           (C) Carbon group             (D) Nitrogen group
     the hydrogen atom?
     (A) The atom's orbital electron is moving too fast
     (B) The photon striking the atom is moving too fast.
     (C) The photon's energy is too small.
     (D) The photon is being repelled by electrostatic force.
14. In which of the following are the chemical species correctly   25. Which of the following molecules contains bonds that have
    ordered from smallest radius to largest radius?                    a bond order of 1.5?
    (A) B < C < N               (B) At < Xe < Kr                       (A) N2        (B) O3       (C) NH3      (D) CO2
                    2-                       +
    (C) CI < S < S              (D) Na < Na < K

                                                                   26.               CCl4, CO2, PCl3, PCl5, SF6
15. Of the following elements, which would be expected to                Which does NOT describe any of the molecules above?
    have chemical properties most similar to those of sulfur, S?         (A) Linear              (B) Octahedral
    (A) Br        (B) CI       (C) P         (D) Se                      (C) Square planar       (D) Tetrahedral

16. Which pair of ions should have the highest lattice energy?     27. According to the VSEPR model, the progressive decrease
           +         -               +      -
    (A) Na and Br              (B) Li and F                            in the bond angles in the series of molecules CH4, NH3,
          +        -                 +       2-
    (C) Cs and F               (D) Li and O                            and H2O is best accounted for by the
                                                                       (A) increasing strength of the bonds
                                                                       (B) decreasing size of the central atom
                                                                       (C) increasing electronegativity of the central atom
17. Which molecule has the weakest bond?                               (D) increasing number of unshared pairs of electrons
    (A) CO     (B) O2        (C) Cl2     (D) N2

                                                                   28. Which of the following is a formula for an acid?
18. Which pair of atoms should form the most polar bond?               (A) CH3–CO–CH3               (B) CH3–CH2–COOH
    (A) F and B               (B) C and O                              (C) CH3–CH2–CH2OH            (D) CH3–CH2–O–CH3
    (C) F and O               (D) N and F

                                                                   29. Which is NOT a structural isomer of 2-methylpentane?
19. Which species has a valid non-octet Lewis structure?               (A) hexane                 (B) 3-methylpentane
    (A) GeCl4 (B) SiF4        (C) NH4
                                           (D) SeCl4                   (C) 2,2-dimethylbutane (D) 4-methylpentane

20. For which molecule are resonance structures necessary to       30. Types of hybridization exhibited by carbon atoms in a
    describe the bonding satisfactorily?                               molecule of propyne, CH3CCH, include which of the
    (A) H2S      (B) SO2       (C) CO2     (D) OF2                     following?
                                                                                                     2                  3
                                                                            I. sp             II. sp            III. sp
                                                                       (A) I only   (B) II only (C) III only (D) I and III only

21. The Lewis structure for SeS2 with zero formal charge has a
     total of
     (A) 2 bonding pairs and 7 nonbonding pairs of electrons.      31. Which of the following best explains why the normal boiling
     (B) 2 bonding pairs and 6 nonbonding pairs of electrons.          point of CCI4(I) (350 K) is higher than the normal boiling
     (C) 3 bonding pairs and 6 nonbonding pairs of electrons.          point of CF4(I) (145 K)?
     (D) 4 bonding pairs and 5 nonbonding pairs of electrons.          (A) The C-CI bonds in CCI4 are less polar than the C-F
                                                                           bonds in CF4.
                                                                       (B) The C-CI bonds in CCI4 are weaker than the C-F
                                                                           bonds in CF4.
                                                                       (C) The mass of the CCI4 molecule is greater than that of
Questions 22-24 refer to the following molecules.                          the CF4 molecule.
    (A) CO       (B) CH4         (C) HF      (D) PH3                   (D) The electron cloud of the CCI4 molecule is more
22. Contains two -bonds                                                   polarizable than that of the CF4 molecule.

23. Has the highest dipole moment (most polar)                     32. Which of the following substances exhibits significant
                                                                       hydrogen bonding in the liquid state?
                                                                       (A) CH2F2                  (B) N2H4
                                                                       (C) CH3OCH3                (D) C2H4
24. Has a molecular geometry that is trigonal pyramidal
Questions 33-34 refer to a various points in time during an        39. At which of the following temperatures and pressures
   experiment conducted at 1.0 atm. Heat is added at a                 would a real gas be most likely to deviate from ideal
   constant rate to a sample of a pure substance that is solid         behavior?
   at time to. The graph below shows the temperature of the                Temperature (K) Pressure (atm)
   sample as a function of time.                                       (A)         100               50
                                                                       (B)         200                5
                                                                       (C)         300              0.01
                                                                       (D)         500              0.01

                                                                   40. In which process are covalent bonds broken?
                                                                       (A) Solid silver melts.
                                                                       (B) Solid potassium chloride melts.
                                                                       (C) Solid carbon (graphite) sublimes.
                                                                       (D) Solid iodine sublimes.

    (A) t1      (B) t2       (C) t3      (D) t5
33. Time when the average distance between particles is
    greatest                                                       41. A closed rigid container contains distilled water and N2(g)
                                                                       at equilibrium. Actions that would increase the
                                                                       concentration of N2(g) in water include which of the
                                                                            I. Shaking the container vigorously
34. Time when the temperature of the substance is between its               II. Raising the temperature of the water
    melting point and its boiling point                                     III. Injecting more N2(g) into the container
                                                                       (A) I only     (B) II only (C) III only (D) I and II only

35. Heat energy is added slowly to a pure solid covalent
    compound at its melting point. About half of the solid melts   42. What is the mole fraction of ethanol in a 6 molal aqueous
    to become a liquid. Which of the following must be true            solution?
    about this process?                                                (A) 0.006 (B) 0.1           (C) 0.08      (D) 0.2
    (A) Covalent bonds are broken as the solid melts.
    (B) The temperature of the solid/liquid mixture remains the
         same while heat is being added.
    (C) The volume of the compound increases as the solid
         melts to become a liquid.                                 43. What additional information is needed to determine the
    (D) The average kinetic energy of the molecules becomes            molality of a 1.0-M glucose (C6H12O6) solution?
         greater as the molecules leave the solid state and            (A) Volume of the solution
         enter the liquid state.                                       (B) Temperature of the solution
                                                                       (C) Solubility of glucose in water
                                                                       (D) Density of the solution

36. Of the following gases, which has the greatest average
    molecular speed at 298 K?
    (A) Cl2       (B) NO       (C) H2S       (D) HCN               44. A solution of toluene (MM = 90 g) in benzene (MM = 80 g)
                                                                       is prepared. The mole fraction of toluene in the solution is
                                                                       0.2. What is the molality of the solution?
                                                                       (A) 0.2        (B) 0.5      (C) 2          (D) 3
37. At approximately what temperature will 40. g of argon gas
    at 2.0 atm occupy a volume of 22.4 L?
    (A) 600 K (B) 550 K (C) 270 K (D) 140 K
                                                                   45. Which of the following aqueous solutions has the highest
                                                                       boiling point at 1.0 atm?
                                                                       (A) 0.20 M CaCl2           (B) 0.25 M Na2SO4
                                                                       (C) 0.30 M NaCl            (D) 0.40 M C6H12O6
38. Three gases in the amounts shown in the table are added
    to a previously evacuated rigid tank.
          Gas                Ar             CH4             N2
         Amount          0.35 mol        0.90 mol       0.25 mol
                                                      o            46.       _CH3OCH3(g) + _O2(g)  _CO2(g) + _ H2O(g)
    If the total pressure in the tank is 3.0 atm at 25 C, the
                                                                         When the equation above is balanced using the lowest
    partial pressure of N2(g) in the tank is closest to
                                                                         whole-number coefficients, the coefficient for O2(g) is
    (A) 0.75 atm                  (B) 0.50 atm
                                                                         (A) 6       (B) 4         (C) 3          (D) 2
    (C) 0.33 atm                  (D) 0.25 atm
47. What mass of KBr (MM = 119 g•mol ) is required to make           55.             2 N2H4 + N2O4  3 N2 + 4 H2O
    250. mL of a 0.400 M KBr solution?                                     What mass of N2 can be produced when 8.0 g of N2H4
    (A) 0.595 g (B) 1.19 g (C) 2.50 g (D) 11.9 g                           (MM = 32 g) and 9.2 g of N2O4 (MM = 92 g) react?
                                                                           (A) 8.4 g    (B) 12.6 g (C) 7.8 g     (D) 10.5 g

48. Na2CO3(s) + 2 HCl(aq)  2 NaCl(aq) + CO2(g) + H2O(l)
    In a laboratory, a student wants to quantitatively collect the   56. A student weighs out 0.0154 mol of pure, dry NaCI in order
    CO2(g) generated by adding Na2CO3(s) to 2.5 M HCI(aq).               to prepare a 0.154 M NaCI solution. Of the following
    The student sets up the apparatus to collect the CO2 gas             pieces of laboratory equipment, which would be most
    over water. The volume of collected gas is much less than            essential for preparing the solution?
    the expected volume because CO2 gas                                  (A) 50 mL volumetric pipet
    (A) is soluble in water                                              (B) 100 mL Erlenmeyer flask
    (B) is produced at a low pressure                                    (C) 100 mL graduated beaker
    (C) is more dense than water vapor                                   (D) 100 mL volumetric flask
    (D) has a larger molar mass than that of N2 gas, the major
         component of air

                                                                     Questions 57-60 The figures show portions of a buret used in a
                                                                        titration 0.0464 moles of monoprotic acid with a solution of
49. Which of the following would produce the LEAST mass of              Ba(OH)2. Figures I and 2 show the level of the Ba(OH)2
    CO2 if completely burned in excess oxygen gas?                      solution at the start and at the endpoint of the titration,
    (A) 10.0 g CH4             (B) 10.0 g CH3OH                         respectively. Phenolphthalein was used as the indicator for
    (C) 10.0 g C2H4            (D) 10.0 g C2H6                          the titration.

50. A solution of RbCl (MM = 121 g•mol ) contains 11.0 %
    RbCl by mass. From the following list, what is needed to
    determine the molarity of RbCl in the solution?
        I. Mass of the sample                                                                     Figure 1       Figure 2
        II. Volume of the sample                                     57. What is the evidence that the endpoint of the titration has
        III. Temperature of the sample                                   been reached?
    (A) I only    (B) II only (C) III only (D) I and II only             (A) The color of the solution in the buret changes from
                                                                             pink to colorless.
                                                                         (B) The color of the solution in the buret changes from
                                                                             blue to red.
                                                                         (C) The color of the contents of the flask changes from
51.            CS2(l) + 3 O2(g)  CO2(g) + 2 SO2(g)                          colorless to pink.
      When 0.60 mol of CS2(l) reacts as completely as possible           (D) The color of the contents of the flask changes from
      with 1.5 mol of O2(g) according to the equation above, the             blue to red
      total number of moles of reaction products is
      (A) 2.4 mol (B) 2.1 mol (C) 1.8 mol (D) 1.5 mol

                                                                     58. The volume of Ba(OH), used to neutralize the acid was
                                                                         closest to
52. What is the empirical formula of a hydrocarbon that is 10 %          (A) 22.80 mL             (B) 23.02 mL
    hydrogen by mass?                                                    (C) 23.20 mL             (D) 29.80 mL
    (A) CH3      (B) C2H5      (C) C3H4      (D) C4H9

                                                                     59. The concentration of the Ba(OH)2 solution is closest to
53. By mixing only 0.15 M HCl and 0.25 M HCl, it is possible to          (A) 1 M     (B) 2 M       (C) 3 M       (D) 4 M
    create all of the following solutions EXCEPT
    (A) 0.21 M (B) 0.18 M (C) 0.16 M (D) 0.14 M

                                                                     60. What could explain why the student calculated a
                                                                         concentration of Ba(OH)2 that was too large?
54.                 8 H2(g) + S8(s)  8 H2S(g)                           (A) An extra drop of phenolphthalein was added.
      When 25.6 g of S8(s) (MM = 256 g•mol ) reacts completely           (B) A small amount of the acid was not transferred to the
      with an excess of H2(g) according to the equation above,               titration flask.
      the volume of H2S(g), measured at 0 C and 1.00 atm,                (C) A drop of Ba(OH)2 remained attached to the buret tip.
      produced is closest to                                             (D) Rinsing the buret with distilled water just before filling
      (A) 30 L     (B) 20 L       (C) 10 L      (D) 5 L                      it with the Ba(OH)2 to be titrated.
                    CaCl2(s)  Ca + 2 Cl
                                     2+     -
61.                                                                66. The purpose of weighing the cup and its contents again at
    For the process of solid calcium chloride dissolving in water,     the end of the experiment was to
    represented above, the entropy change might be expected to         (A) determine the mass of solute that was added.
    be positive. However, S for the process is actually negative.     (B) determine the mass of the thermometer.
    Which best helps to account for the net loss of entropy?           (C) determine the mass of water that evaporated.
           -                                      2+
    (A) Cl ions are much larger in size than Ca ions.                  (D) verify the mass of water that was cooled.
    (B) The particles in solid calcium chloride are more
         ordered than are particles in amorphous solids.
                                              2+        -
    (C) Water molecules in the hydrated Ca and Cl ions are
         more ordered than they are in the pure water.             67. Suppose that during the experiment, a significant amount
                 2+       -
    (D) The Ca and Cl ions are more free to move around in             of solution spilled from the polystyrene cup before all of the
         solution than they are in CaCl2(s)                            solute dissolved. How does this affect the calculated value
                                                                       for the heat of solution of the ionic compound?
                                                                       (A) The calculated value is too large because less water
                                                                            was cooled as the remaining solute dissolved.
62. For which of the processes does entropy decrease (S < 0)?         (B) The calculated value is too large because some solute
    (A) H2O(s)  H2O(l)                                                     was lost with the spilled solution.
    (B) Br2(l)  Br2(g)                                                (C) The calculated value is too small because less solute
    (C) Crystallization of I2(s) from an ethanol solution                   was dissolved than the student assumed.
    (D) Thermal expansion of a balloon filled with CO2(g)              (D) The calculated value is too small because the total
                                                                            mass of the calorimeter contents was too small.

63. What mass of Cu(s) would be produced if 0.40 mol of
    Cu2O(s) was reduced completely with excess H2(g)?                68.                        Pb(s)  Pb(l)
    (A) 13 g    (B) 25 g     (C) 38 g     (D) 51 g                         Which of the following is true for the process represented
                                                                           above at 327 C and 1 atm? (The normal melting point for
                                                                           Pb(s) is 327 (C))
                                                                           (A) H = 0                   (B) TS = 0
                                                                           (C) S < 0                   (D) H = TS
64. A certain reaction is spontaneous at temperatures below
    400 K but is not spontaneous at temperatures above 400
    K. If H for the reaction is -20 kJ•mol and it is assumed
              o                            -1

    that H and S do not change appreciably with
            o         o

    temperature, then the value of S for the reaction is
                                       o                             69.                  C(diamond)  C(graphite)
    (A) -50 J•mol •K
                        -1                       -1
                                (B) -20.0 J•mol •K
                                                       -1                  For the reaction represented above, the standard Gibbs
                                                                           free energy change, G 298, has a value of -2.90 kJ•mol .
                                                                                                   o                               -1
                     -1    -1                 -1    -1
    (C) -0.05 J•mol •K          (D) -20 J•mol •K
                                                                           Which of the following best accounts for the observation
                                                                           that the reaction does NOT occur (i.e. diamond is stable)
                                                                           at 298 K and 1.00 atm?
                                                                           (A) S for the reaction is positive.
65.                          ZX+Y
                                                                           (B) The activation energy, Ea, for the reaction is very
      A pure substance Z decomposes into two products, X and
      Y, as shown by the equation. Which of the following graphs                                                       o
                                                                           (C) The reaction is slightly exothermic (H < 0).
      of the concentration of Z versus time is consistent with the
                                                                           (D) Diamond has a density greater than that of graphite.
      rate of the reaction being first order with respect to Z?
      (A)                          (B)

                                                                     70. When a solution is formed by adding some methanol,
                                                                         CH3OH, to water, processes that are endothermic include
      (C)                       (D)                                      which of the following?
                                                                             I. Methanol molecules move water molecules apart
                                                                                  as the methanol goes into solution.
                                                                             II. Water molecules move methanol molecules apart
                                                                                  as the methanol goes into solution.
                                                                             III. Intermolecular attractions form between
                                                                                  molecules of water and methanol as the methanol
                                                                                  goes into solution.
                                                                         (A) I only    (B) II only (C) III only (D) I and II only
Questions 66-67 refer to an experiment to determine the heat
   of solution of an ionic solid. A student used a calorimeter
   consisting of a polystyrene cup and a thermometer. The
   cup was weighed, then filled halfway with water, then
   weighed again. The temperature of the water was                                                      Answers
   measured, and some of the ionic solid was added to the            #                                 Explanation
   cup. The mixture was gently stirred until all of the solute             Average = (Mass1 x Abundance1) + (Mass2 x Abundance2)
                                                                     1   D
   dissolved and the lowest temperature reached by the water               63.5 = (63)(1 – x) + (65)(x) = 63 – 63x + 65 x  x = 0.25 (25 %)
                                                                     2   D 3920Ca  3919K + 01
   in the cup was recorded. The cup and its contents were
                                                                           It takes 3 half-lives to reduce the radioactivity to 1/8 (1.25/10.0).
   weighed again.                                                    3   C
                                                                           195 days/3 = 65 days
        From the diagram: E6 = -0.38 eV and E2 = -3.40 eV                               Gas solubility increases with greater partial pressure of the gas in
4   B                                                                            41 C
        E = E2 – E6 = -3.40 eV – (-0.38 eV) = -3.02 eV                                 the container or lower temperature.
        The electron can only absorb energy that will move it to a higher               6 molal = 6 mol ethanol in 1000 g H2O
5   C   energy level. 9.4 eV is not enough energy (the minimum needed            42 B   1000 g H2O x 1 mol/18 g = 55 mol H2O
        is -3.40 eV – (-13.60 eV) = 10.2 eV).                                            mole fraction = 6/(6 + 55) = 0.1
        The orbital diagram for C,1s() 2s() 2p()()( ), has two                  Molality is moles solute/kg solvent. Molarity is moles solute/L
6   C
        unpaired electrons (Hund's rule) = paramagnetic.                         43 D   solution. To determine kg solvent from L solution, you need to
        Pauli states that no orbital can contain electrons with the same                know density; then subtract g solute.
7   B                                                                                   0.2 mole fraction = 0.2 mol toluene in 0.8 benzene
        spin. Since two spins, this limits the number to two electrons.
        Heisenberg states that the wave nature of matter (DeBroglie)             44 D   0.8 mole x 80 g/1 mol = 60 g benzene
8   A                                                                                   molality = 0.2 mol/0.060 kg = 3 m
        limits what we can know about position and velocity.
        Electron # 31 is located in the 4th row (n = 4), 13th column (p          45 B
                                                                                        The highest boiling point = highest concentration of ions.
9   C   section, l= 1), which limits ml = 1, 0 or -1 and ms = +½ or -½                (A) .2 x 3 = .6, (B) .25 x 3 = .75, (C) .3 x 2 = .6, (D) .4 x 1 = .4
        (4, 1, 1, ½) fits requirement                                            46 C   1 CH3OCH3(g) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
        1s() 2s() 2p()(    ): The 2p electron is in an excited   47 D   0.250 L x 0.400 mol/L = 0.1 mol KBr x 119 g/mol = 11.9 g
10 B
        state, otherwise it would go into the 2s sublevel.                              If CO2 is soluble in water, then some gas would remain in the
                                                                                 48 A
        1s() 2s() 2p()()(): The 2 2s electrons and 3 2p                    water and not bubble into the gas collecting bottle.
11 C                                                                                    CH3OH has the lowest proportion of C (12/32)  given equal
        electrons are in the valence shell (highest energy level)  five.        49 B
        1s(): The first ionized electron is from the 1s sublevel. It takes            masses; CH3OH would generate the least amount of CO2.
12 A                                                                                    molarity = mol solute/volume solution (L). The mass is needed to
        the most energy to remove electrons that are close to nucleus.
        The biggest jump in ionization energy occurs between 4 and 5,            50 D   determine the number of moles of solute. The volume is needed
13 C                                                                                    to determine the volume of solution.
        which means 4 valence electrons  Carbon group.
        Atomic radius increases going left and down in periodic table.                  0.6 mol CS2 x 3 mol Products/1 mol CS2 = 1.8 mol Products
14 C                                                                             51 D   1.5 mol O2 x 3 mol Products/3 mol O2 = 1.5 mol Products
        Anion is larger than atom and cation is smaller than atom.
        Elements in the same column in the periodic table have similar                  1.5 mol Products is the lesser number.
15 D                                                                                    Assume 100 g of compound
        chemical properties.
        Lattice energy is a measure of ionic bond strength, which is             52 C   10 g H x 1 mol/1 g = 10 mol/7.5 = 1.33 x 3 = 4
16 D                                                                                    90 g C x 1 mol/12 g = 7.5 mol/7.5 = 1 x 3 = 3
        proportional to charge and inversely proportional to size.
                                                                                        The resulting solution must have a concentration between the two
17 C    Single bonds are the weakest (CO, O=O, Cl–Cl, NN)  Cl2.               53 D
                                                                                        solutions added together. 0.14 M is less then both.
        Most polar bond forms between atoms with the greatest
18 A                                                                                    25.6 g S8 x 256 g/mol x 8 mol H2S/1 mol S8 = 0.8 mol
        electronegativity difference (greatest gap on the periodic table).       54 B
                                                                                        0.8 mol x 22.4 L/mol = 20 L
        SeCl4 has 34 valence electrons, which require an expanded octet
19 D                                                                                    0.25 mol N2H4 x 3 mol N2 x 28 g N2 = 10.5 g
        system (sp3d) to accommodate all the electrons.
                                                                                 55 A                      2 mol N2H4 1 mol N2
        Only SO2 has a single and double bond, which can exchange
                                                                                        0.1 mol N2O4 x 3 mol N2/1 mol N2O4 x 28 g N2 = 8.4 g
20 B    places, thus forming resonance forms. (H2S and OF2: 2 single
                                                                                        0.0154 mol NaCl x 1 L/0.154 mol = 0.1 L (100 mL)
        bonds, CO2: 2 double bonds)
                                                                                 56 D   The most accurate way to measure 0.1 L of solution is to use a
        ::S=Se:=S:: has zero formal charge. There are 4 bonds and 5
21 D                                                                                    volumetric flask.
        pairs of nonbonding electrons.
                                                                                 57 C   Phenolphthalein changes from clear (acid) to pink (base)
        CO: The triple bond between C and O is composed of one
22 A                                                                                    Final volume – Initial volume = Change in volume
        sigma bond and two pi bonds.                                             58 C
                                                                                        35.75 mL – 12.55 mL = 23.20 mL
        H-F: The electronegativity difference is greatest between H and F
23 C                                                                                    0.0464 mol H+ x 1 mol OH- x 1 mol B(A).. = 0.0232 mol B(A)..
         the most polar, which produces the highest dipole moment.              59 A                       1 mol H+ 2 mol OH-
        PH3: The three H are pushed away from the pair of non-bonding                   0.0232 mol B(A)../0.0232 L = 1 M
24 D
        electrons around phosphorus resulting in a pyramidal structure.                 MBa(OH)2 = (½ mol H+)/VBa(OH)2
        A bond order of 1.5 means 1 sigma bond and 50% share of a pi             60 B    too large MBa(OH)2 = too small VBa(OH)2
25 B
        bond, which is the case for O3 (O=O–O).                                         Titrating less acid would result in smaller VNaOH
        CCl4 (tetrahedron), CO2 (linear), PCl3 (trigonal pyramid), PCl5
26 C                                                                                    Dissolving involves two process; (1) separation into ions, which
        (trigonal bipyramid), SF6 (octahedron)
                                                                                 61 C   increases disorder (+S) and (2) ions combining with water
        The non-bonding electron pairs take up more space than bonding
27 D                                                                                    (solvation), which decreases disorder (-S).
        pairs  H2O (2 pairs) < NH3 (1 pair) < CH4 (0 pair).
                                                                                        Disorder decreases when I2(aq)  I2(s). Disorder increases
        Acids contain the COOH functional group  (B) (a is a ketone, c
28 B                                                                             62 C   when s  l  g (A) and (B). Disorder also increases when gas
        is an alcohol, and d is an ether)
                                                                                        molecules spread out (D).
        4-methylpentane is the same as 2-methylpentane because you
29 D                                                                                    Cu2O + H2  2 Cu + H2O (balancing wasn't necessary because
        number from the closest end  4 becomes 2.
                                                                                 63 D   mole Cu in reactants and products are equal)
30 D    C1H3–C2C3H: C1 is sp3, C2 is sp, C3 is sp                                      0.80 mol Cu x 63.5 g/mol = 51 g
        Both molecules are non-polar, but the larger molar mass of CCl4
                                                                                        Tthreshold = H/S
31 D    means that there are more electrons, which are more polarizable
                                                                                 64 A   S = H/Tthreshold = -20 kJ•mol-1/400 = -0.05 kJ•mol-1•K-1
         generating a stronger dispersion force.
                                                                                        -0.05 kJ•mol-1•K-1 x 1000 J/1 kJ = -50 J•mol-1•K-1
        Hydrogen bonding occurs when H is bonded to N, O or F. Only
32 B                                                                                    For a first order reaction, the straight line graph is ln[Z] vs. t.
        N2H4 has that arrangement. (CH2F2: H is not bonding to the F)            65 D
                                                                                        (zero order is [Z] vs. t and second order is 1/[Z] vs. t)
33 D    Farthest from each other in the gaseous phase, which is at t 5.
                                                                                        At the end of the experiment, the cup contained solute and water.
        Melting occurs along 1st plateau (t2) and boiling along 2nd plateau      66 A   If this value is subtracted from the mass of the cup and water,
34 C
        (t4)  the time between these two temperatures is t3.                           then the difference is the mass of the solute.
        (a) Covalent bonds aren't broken if its molecular.                              The heat needed to dissolve the remaining solute had to come
35 B    (c) Volume only increases if liquid state is less dense.                 67 A   from less water, which would make T greater than it should have
        (d) Temperature doesn't increase  KE is not greater.                           been (H = -mcT) H would be too large.
36 D    At the same temperature, lighter molecules have greater speed.
                                                                                 68 D   At the normal melting point: G = 0 = H – TS H = TS
        40 g of Ar = 1 mol. One mole at STP = 22.4 L. Since P is 2 x
37 B                                                                                    The reaction is spontaneous, but it must not occur at a fast rate.
        standard, then T has to be 2 x standard (V = nRT/P)  2 x 273 K          69 B   This could be because the activation energy is so high, that it
38 B    PN2 = XN2Ptot = (0.25/(0.35 + 0.90 + 0.25))(3.0 atm) = 0.50 atm                 takes too much energy to start the process.
        Real gases deviated from ideal behavior at low temperatures                     Breaking solute-solute bonds in methanol and water is
39 A
        (near their boiling point) and high pressure.                            70 D   endothermic, but forming solute-solute bonds between methanol
        (A) metallic bond, (B) ionic bond, (C) covalent bond, and (D)                   and water is exothermic.
40 C
        molecular bond.

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