LPC, Chem 1A Final Exam Review, Fall 2002 - DOC by rua13781

VIEWS: 1,284 PAGES: 11

									BCC, Fall 2007
Chem 1A Final Review

Part A : Multiple-choice questions.

1.    The boiling point of chlorine gas is 239.2 K at 1 atm. What is this temperature in Fahrenheit (oF)?
      (a) 462.6oF        (b) –29.2oF           (c) –34.0oF           (d) 93.2oF

2.    A cylindrical metal rod of uniform diameter measures 122.0 cm long and weighs 934.0 grams. If the
      diameter of the rod is 1.90 cm, calculate the density of metal in g/cm3.

      (a) 2.70 g/cm3     (b) 1.35 g/cm3              (c) 2.70 x 10-3 g/cm3    (d) 2.70 x 103 g/cm3

3.    Which of the following involves a chemical change?
      (a) Sugar dissolves in water;       (c) Evaporation of rubbing alcohol;
      (b) The wood is rotting away;       (d) Sulfur melts at 115oC.

4.    The number of protons, neutrons, and electrons, respectively, in the ionic species     239
                                                                                              94   Pu4+ is:
      (a) 94, 239, 90;      (b) 94, 145, 90;          (c) 94, 145, 98;        (d) 94, 239, 94;

5.    A compound with an empirical formula C2H3 may have which of the following molecular formula?
      (a) C3H4           (b) C5H8         (b) C12H18           (d) C8H14

6.    The formula of ammonium molybdate is (NH4)2MoO4. What is the formula of aluminum molybdate?
      (a) AlMoO4         (b) Al4(MoO4)3              (c) Al2(MoO4)            (d) Al2(MoO4)3

7.    Which is the correct formula of ammonium hydrogen phosphate ?
      (a) (NH4)3HPO4        (b) (NH4)2HPO4             (c) (NH3)2HPO4         (d) (NH3)3HPO4

8.    A compound with formula Cr2(SO4)3 is named
      (a) Dichromium trisulfate           (c) Chromium(III) sulfate
      (b) Chromium(II) sulfate            (d) Chromium(III) trisulfate

9.    Boron reacts with oxygen gas to form a product having which formula?
      (a) B2O            (b) BO3          (c) B3O2           (d) B2O3

10.   Name a compound with formula H2SO3.
      (a) Dihydrogen sulfite              (c) Sulfurous acid
      (b) Dihydrosulfitic acid            (d) Hydrosulfuric acid

11.   For the reaction between solid CaCO3 and aqueous HCl solution, the net ionic equation is:
      (a) Ca2+(aq) + 2Cl-(aq)  CaCl2(s);
      (b) 2H+(aq) + CO32-(aq)  H2O(l) + CO2(g);
      (c) CaCO3(s) + 2H+(aq)  Ca2+(aq) + H2O(l) + CO2(g);
      (d) 2HCl(aq) + CO32-(aq)  H2O(l) + CO2(g) + 2Cl-(aq);

12.   Which solution when reacted with aqueous sodium phosphate, Na3PO4, will yield a precipitate?
      (c) Barium chloride          (b) Calcium acetate       (a) Silver nitrate       (d) All of them

BCC, Fall 2007
Chem 1A Final Review

13.   Which compound forms a strong electrolyte when dissolved in aqueous solution?
      (a) (NH4)3PO4                (b) H3PO4                 (c) NH4OH              (d) CH3OH

14.   A student needs to prepare 2.00 L of 0.100 M Na2CO3 (molar mass = 106 g/mol). The best procedure
      is to weigh out:
      (a) 10.6 g of Na2CO3, add 2.00 L of water and mix well to dissolve the solid.
      (b) 21.2 g of Na2CO3, add 2.00 L of water and mix well to dissolve the solid.
      (c) 10.6 g of Na2CO3 and add enough water to make 2.00 L of homogeneous solution.
      (d) 21.2 g of Na2CO3 and add enough water to make 2.00 L of homogeneous solution.

15.   For the reaction between strong nitric acid and potassium hydroxide (a strong base), the correct net
      ionic equation is:

      (a) H+(aq) + OH-(aq)  H2O(l);
      (b) HNO3(aq) + OH-(aq)  H2O(l) + NO3-(aq);
      (c) H+(aq) + NaOH(aq)  H2O(l) + Na+(aq);
      (d) HNO3(aq) + NaOH(aq)  H2O(l) + Na+(aq) + NO3 (aq)

16.   For an acid-base reaction between acetic acid (a weak acid) and sodium hydroxide (a strong base), the
      correct net ionic equation is:

      (a) H+(aq) + OH-(aq)  H2O(l);
      (b) HC2H3O2(aq) + OH (aq)  H2O(l) + C2H3O2-(aq);
      (c) H+(aq) + NaOH(aq)  H2O(l) + Na+(aq);
      (d) HC2H3O2(aq) + NaOH(aq)  H2O(l) + Na+(aq) + C2H3O2 (aq)

17.   How many grams of KOH are present in 400. mL of 0.250 M KOH solution?
      (a) 5.61 g         (b) 14.0 g            (c) 0.100 g             (d) 100. g

18.   A chemist needs 2.5 L of 0.24 M HCl. What volume of 12 M HCl must be diluted to make this
      (a) 1.2 L        (b) 0.60 L         (c) 50. mL (d) 5.0 mL

19.   A sample of gas collected at 22oC and 600. torr has a volume of 2.55 liters. What volume would the
      gas occupy at STP?
      (a) 1.86 L         (b) 2.18 L       (c) 2.99 L         (d) 3.49 L

20.   A 25-liter gas tank contains 0.50 mole of H2 gas and 0.50 mole of N2 gas at 20oC. Which of the
      following statements is true?
      (a) N2 gas exerts a greater pressure due to its heavier molecules;
      (b) N2 gas has the greater average kinetic energy;
      (c) H2 gas has the greater root-mean-square speed;
      (d) H2 gas exerts a greater pressure because of its higher frequency of collisions.

21.   Which of these gases has the greatest rate of effusion under the same conditions?
      (a) NO             (b) HCl          (c) NH3            (d) H2S

BCC, Fall 2007
Chem 1A Final Review

22.   Nitrogen and hydrogen gases react to form ammonia gas as follows:
                  N2(g) + 3H2(g)  2NH3(g);
      At a certain temperature and pressure, 7.0 L of N2 is reacted with 21.0 L of H2. If all N2 and H2 are
      consumed, what volume of NH3 will be produced at the same temperature and pressure?
      (a) 7.0 L           (b) 14 L        (c) 21 L           (d) 28 L

23.   What is the algebraic sign (positive “+” or negative “–“) for q and w in the following process at 1 atm
      and 100oC?
                        H2O(l)  H2O(g)
      (a) q is positive, w is negative               (b) q is negative, w is positive
      (c) both of them are positive                  (d) both of them are negative

24.   A sample of ideal gas at 25oC expands from 1.00 liters to 10.00 liters against a constant pressure of
      1.00 atm. How much work (in Joules) is performed on the surroundings? (1 L.atm = 101.3 J)

      (a) 912 J           (b) 1013 J      (c) 2530 J         (d) 253 J

25.   When 100.0 grams of water at 20.0oC is mixed with 25.0 grams of water at a certain temperature, the
      final temperature of the resulting mixture is 32.0oC. What was the initial temperature of the second
      water sample? (specific heat of water = 4.184 J/g.oC)
      (a) 80.0oC          (b) 68.0oC      (c) 48.0oC         (d) 41.6oC

26.   A 40.2 g sample of a metal is heated to 99.3oC and then placed in a calorimeter containing 120.0 g of
      water (s = 4.18 J/g.oC) at 21.8oC. The final temperature of water and metal is 24.5oC. Identify the
      metal used?

      (a) Aluminum (s = 0.89 J/g.oC)                 (b) Copper (s = 0.38 J/g.oC)
      (c) Iron (s = 0.45 J/g.oC)                     (d) Lead (s = 0.14 J/g.oC)

27.   The total volume of hydrogen gas to fill the Hindenburg was 2.00 x 108 L at 1.00 atm and 25.0oC.
      How much energy was evolved when it burned?

                  H2(g) + ½ O2(g)  H2O(l); H = -286 kJ

      (a) 2.86 x 104 kJ           (b) 8.18 x 106 kJ          (c) 2.34 x 109 kJ          (d) 5.72 x 1010 kJ

28.   The heat of formation of Fe2O3(s) is –826 kJ/mol. Calculate the enthalpy change for the reaction:
        4Fe(s) + 3 O2(g)  2Fe2O3(s) when 55.8 g of iron is reacted.
      (a) -206 kJ         (b) -413 kJ         (c) -826 kJ           (d) -1650 kJ

29.   Which of the following is an exothermic process?
      (a) O  O+ + e-;            (b) O-  O + e-;           (c) O2-  O- + e-;         (d) none of them;

30.   Which of the following processes requires the most amount of energy?
                           -                             -                          -                        -
      (a) Al+  Al2+ + e ;        (b) Al2+  Al3+ + e ;      (c) Mg+  Mg2+ + e ;        (d) Na+  Na2+ + e ;

BCC, Fall 2007
Chem 1A Final Review

31.   As the strength of the attractive intermolecular forces increases, which one of the following will also
      (a) The enthalpy of vaporization
      (b) The normal boiling temperature
      (c) The extent of deviations from the ideal gas behavior
      (d) The vapor pressure of a liquid

32.   Hydrogen bonds account for which of the following observation?
      (a) Hydrogen forms stable diatomic molecules
      (b) Hydrogen gas has a very low boiling point
      (c) Water is a liquid at room temperature
      (d) Water is denser than ice

33.   Which of the following molecules is not expected to exhibit hydrogen bondings in the liquid state?
      (a) CH3F           (b) CH3NH2                (b) CH3OH                  (d) None of them

34.   For each of the following sets, which substance would you expect to have the highest boiling point?
      (i)    (a) CH4             (b) CF4           (c) SiH4           (d) SiF4

      (ii)   (a) NH3             (b) PH3           (c) AsH3           (d) SbH3

      (iii) (a) C2H4             (b) N2H4          (c) CH4            (d) NH3

35.   For each of the following sets, which substance is expected to have the highest melting point?
      (i)    (a) CO2             (b) KO2           (c) NO2            (d) SO2

      (ii)   (a) PbO2            (b) SO2           (c) SiO2           (d) TiO2

      (iii) (a) Br2              (b) I2            (c) P4             (d) S8

36.   On a relative basis, the weaker the intermolecular forces in a substance,
      (a) the higher the surface tension of the liquid
      (b) the higher the vapor pressure of the liquid
      (c) the higher the viscosity
      (d) None of the above.

37.   CO2 molecules in dry ice are attracted to one another by what forces
      (a) London dispersion forces only
      (b) London dispersion forces and permanent dipole-dipole attractions
      (c) Permanent dipole-dipole attractions only
      (d) Permanent dipole-dipole attractions and ionic bonds.

38.   If the vapor pressure of water at 100oC is 760.0 torr and its enthalpy of vaporization is 40.7 kJ/mol,
      calculate its vapor pressure at 37oC. (R = 8.314 J/mol.K)

      (a) 699 torr       (b) 281 torr      (c) 25.4 torr      (d) 52.8 torr

39.   The molar volume of a certain form of solid lead is 18 cm3/mol. Assuming lead forms cubic closest
      packed lattice structure, determine the following:

BCC, Fall 2007
Chem 1A Final Review

      (i) The number of lead atoms per unit cell
        (a) 4            (b) 6            (c) 8              (d) 12

      (ii) The volume of a single cell
        (a) 1.20 x 106 pm3        (b) 1.20 x 108 pm3         (c) 1.20 x 1010 pm3       (d) 1.20 x 1012 pm3

      (iii) The radius of a Pb atom.
        (a) 1.74 pm               (b) 17.4 pm                (c) 174 pm                (d) 1740 pm

40.   Which of the following statements about solid copper, which forms face-centered cubic unit cell, is
      (a) There are four Cu atoms per unit cell
      (b) The solid has a cubic closest-pack structure
      (c) The number of atoms surrounding each Cu atom is 12
      (d) The length of a body diagonal is four times the radius of Cu atom.

41.   Chromium metal crystallizes as a body-centered cubic lattice. The relationship between the radius of
      a chromium atom ® and the length of an edge of the unit cell (S) is:
      (a) r = (S3)/4             (b) r = (S2)/4            (c) r = S/2           (d) r = (3S)/4

42.   Chromium metal crystallizes as a body-centered cubic lattice. If the atomic radius of Cr is 125 pm,
      what is density of chromium metal in g/cm3?
      (a) 5.52 g/cm3              (b) 7.18 g/cm3             (c) 7.81 g/cm3            (d) 8.92 g/cm3

43.   Calcium fluoride (CaF2) crystallizes in a structure in which the Ca2+ ions occupy the face-centered
      lattice points and F ions fill up the tetrahedral holes. What is the number of fluoride ions in the unit
      (a) 2              (b) 4             (c) 6            (d) 8

44.   A certain metal oxide crystallizes in such a way that the O2- ions form the face-centered cubic
      structure and the metal Mn+ ions occupy the tetrahedral holes. Which is the most probable formula of
      the metal oxide?
      (a) M2O            (b) MO           (c) MO2            (d) MO3

45.   Silver chloride crystallizes with the sodium chloride (rock salt) structure. If the length of the unit cell
      edge is 555 pm, what is the density of AgCl?
      (a) 1.39 g/cm3     (b) 2.78 g/cm3              (c) 5.57 g/cm3            (d) 1.39 x 106 g/cm3

46.   At 1.00 atm and 0oC, which phase(s) of H2O can exist?
      (a) Ice only       (b) Ice and water           (c) Ice and water vapor           (d) water and water vapor

47.   Which of the following is a covalent network solid?
      (a) BaO2           (b) PbO2         (c) SiO2           (d) TiO2

48.   Which pair compounds consists of an ionic solid and a molecular solid, respectively?
      (a) Al2O3 and B2O3          (b) BaCl2 and CoCl2        (c) CO2 and SO2           (d) B2O3 and Cr2O3

BCC, Fall 2007
Chem 1A Final Review

49.   The substance with the highest melting temperature in the following list is:
      (a) H2O            (b) CO2              (c) MgF2           (d) SiF4

50.   Which compound has the greatest lattice energy ?
      (a) LiF            (b) NaF              (c) MgF2           (d) CaF2

51.   When a nonpolar liquid displays a convex meniscus, which of the following explains this behavior?
      (a) It has a low surface tension, and therefore clings to the glass.
      (b) The cohesive forces are stronger that the adhesive forces toward the glass.
      (c) The adhesive forces toward the glass are stronger than the cohesive forces.
      (d) The liquid has a low viscosity.

52.   You are given the following boiling point data:
      (a) Water, H2O: 100oC;                          (b) Methanol, CH3OH: 65.0oC;
      (c) ethanol, CH3CH2OH: 78.5oC;                  (d) diethyl ether, CH3CH2-O-CH2CH3: 34.5oC.
      Which one of the above liquids would you expect to have the highest vapor pressure at room

53.   How much energy is needed to convert 64.0 g of ice at 0.00oC to water at 75oC?
      (specific heat of ice = 2.10 J/g.oC; specific heat of water = 4.18 J/g.oC; heat of fusion = 333 J/g, and
      heat of vaporization = 2260 J/g)
      (a) 10.1 kJ        (b) 20.7 kJ          (c) 31.4 kJ        (d) 41.4 kJ

54.   When 5.00 g of benzene (C6H6) is completely vaporized at a constant pressure of 1.00oC and at its
      normal boiling point of 353.0 K, 1.97 kJ of heat is absorbed and the volume change is +1.85 L.
      Calculate the molar enthalpy of vaporization (Hvap) for benzene.
      (a) 9.85 kJ/mol        (b) 30.8 kJ/mol                     (c) 36.6 kJ/mol           (d) 44.0 kJ/mol

55.   The triple point of iodine is at 90 torr and 115oC. This means that liquid I2
      (a) is more dense than solid I2;                (b) cannot exist above 115oC;
      (c) cannot exist at 1 atm pressure;             (d) cannot have a vapor pressure less than 90 torr.

56.   The triple point of CO2 is at 5.2 atm and –57oC. Under conditions of 1.00 atm pressure and 20oC,
      solid CO2 will:
      (a) remain solid             (b) boil           (c) melt              (d) sublime.

57.   When NaOH dissolves in water, the resulting solution becomes warm. Which of the following
      equation represents the correct dissolution process for NaOH?

      (a) NaOH(s) Na+(aq) + OH-(aq) + heat;                    (c) NaOH(s) + heat  Na+(aq) + O2-(aq) + H+(aq);
      (b) NaOH(s) + heat  Na+(aq) + OH-(aq) ;                  (d) Na+(aq) + OH-(aq)  NaOH(aq) + heat.

58.   Sodium chloride is soluble in water because of the strong interactions between Na+ and Cl- ions with
      H2O molecules. These interactions are called _______________ attractions.
      (a) dipole-dipole                       (c) ion-dipole
      (b) dipole-induced dipole               (d) London dispersion

BCC, Fall 2007
Chem 1A Final Review

59.   Which of these substances is expected to be most soluble in hexane, C6H14 (a nonpolar solvent)?
      (a) NaF             (b) SiF4          (c) AlF3          (d) SF2

60.   Which of the following solutions, at the same concentration, will have the highest boiling point?
      (a) Al(NO3)3                   (b) Ca(NO3)2         (c) NaNO3             (d) CH3NO2

61.   Compared to pure water, an aqueous solution of sodium chloride will exhibit:
      (a) lower vapor pressure, lower freezing point and lower boiling point;
      (b) higher vapor pressure, higher freezing point and higher boiling point;
      (c) lower vapor pressure and lower freezing point, but a higher boiling point;
      (d) higher freezing point, but lower vapor pressure and lower boiling point

62.   What is the molality of a solution of 50.0 g propanol (CH3CH2CH2OH) in 152 mL of water, if the
      density of water is 1.00 g/mL?

      (a) 5.47 m          (b) 0.00547 m                (c) 0.329 m          (d) 0.833 m

63.   An aqueous solution is 9.0% glucose (C6H12O6) by mass. What is the molality of the solution?
      (a) 0.50 m          (b) 0.55 m        (c) 0.055 m       (d) 0.090 m

64.   A 26.35% solution of Mg(NO3)2 has a density of 1.108 g/mL. What is the molarity of the solution?
      (a) 0.1776 M        (b) 1.968 M       (c) 7.470 M       (d) 2.412 M

65.   A 26.35% solution of Mg(NO3)2 has a density of 1.108 g/mL. What is the molality of the solution?
      (a) 2.412 m         (b) 1.776 m       (c) 0.3578 m      (d) 3.578 m

66.   A 20.0-g sample of methyl alcohol (CH3OH, molar mass = 32.0 g/mol) was dissolved in 30.0 g of
      water. The mole fraction of CH3OH is:
      (a) 0.273           (b) 0.400         (c) 0.625         (d) 0.728

67.   Rank the following compounds according to their increasing solubility in water.
      CH3CH2CH2CH3(I)                CH3CH2OCH2CH3(II)          CH3CH2OH(III)             CH3OH(IV)
      (a) I < III < IV < IV < II            (b) I < II < IV < III
      (c) III < IV < II < I                 (d) I < II < III < IV

68.   When 0.800 g of NH4NO3 was added to 150.0 g of water in a styrofoam cup, the temperature dropped
      by 0.413oC. The heat capacity of H2O is 4.18 J/g.oC. Assuming that the specific heat of the solution
      equals that of pure water and that the calorimeter neither absorbs nor leaks heat. Calculate the molar
      heat of solution for solid NH4NO3.

      (a) –2.60 kJ/mol               (b) +2.60 kJ/mol         (c) +26.0 kJ/mol            (d) +260. kJ/mol

69.   Which of the following mixtures is most likely to form an ideal solution?
      (a) water and isopropanol (CH3CH(OH)CH3)                (b) methanol (CH3OH) and ethanol (CH3CH2OH)
      (c) benzene (C6H6) and octane (C8H18)                   (d) ethanol (CH3CH2OH) and benzene (C6H6)

BCC, Fall 2007
Chem 1A Final Review

70.   At 40oC, heptane has a vapor pressure of 92.0 torr and octane has a vapor pressure of 31.2 torr.
      Assuming ideal behavior, what is the vapor pressure of a solution that contains twice as many moles
      of heptane as octane?

      (a) 51.5 torr     (b) 61.6 torr    (c) 71.7 torr    (d) 76.8 torr

71.   Thyroxine, and important hormone that controls the rate of metabolism in the body, can be isolated
      from the thyroid gland. If 0.455 g of thyroxine is dissolved in 10.0 g of benzene, the freezing point of
      the solution is 5.144oC. The freezing point of pure benzene is 5.444oC and the freezing point
      depression constant (Kf) is 5.12oC/m. What is the molar mass of thyroxine?

      (a) 2330 g/mol    (b) 777 g/mol             (c) 376 g/mol            (d) 285 g/mol

72.   A 1% sugar solution and a 10% sugar solution are separated by a semi-permeable membrane. There
      will be a net flow of which of the following across the membrane?
      (a) sugar molecules from the 10% solution to the 1% solution;
      (b) water molecules from the 10% solution to the 1% solution;
      (c) sugar molecules from the 1% solution to the 10% solution;
      (d) water molecules from the 1% solution to the 10% solution

73.   A 2.50-g sample of a hydrocarbon solute (molar mass = 340 g/mole) is dissolved in benzene to make
      a 350-mL solution. What is the osmotic pressure of the solution at 20.0oC?

      (a) 110. torr     (b) 220. torr    (c) 380. torr    (d) 440. torr

74.   What is the osmotic pressure of 0.10 M NaCl solution at 25oC ?
      (a) 2.4 atm       (b) 4.9 atm      (c) 0.41 atm     (d) 0.82 atm

75.   A 1.40-g sample of synthetic organic polymer was dissolved in enough benzene to make 100. mL
      solution, which exhibits an osmotic pressure of 18.6 torr at 25oC. What is the molar mass of the
     (a) 5.72 x 103 g/mol (b) 1.40 x 104 g/mol (c) 3.39 x 105 g/mol (d) 1.06 x 107 g/mol

Part B:

B1.   Give the systematic name for each of the following compounds:

      (a) KH2PO4:______________________________               (f) N2O:_____________________________

      (b) (NH4)2CO3:____________________________              (g) HClO4: ___________________________

      (c) Pb(NO3)2 :_____________________________             (h) Sn(C2H3O2)2:_______________________

      (d) CoCl2.6H2O:___________________________              (i) B2O3 :_____________________________

      (e) Al2(SO4)3: _____________________________            (j) H3PO4:____________________________

BCC, Fall 2007
Chem 1A Final Review

B2.   Write the correct formula for each of the following compounds:

      (a) Ammonium dichromate:_______________               (f) Acetic acid:___________

      (b) Sodium hypochlorite:______________                (g) Calcium phosphate:___________

      (c) Copper(II) sulfate pentahydrate: __________       (h) Dinitrogen pentoxide:_________

      (d) Mercury(I) nitrate: ________________              (i) Hydrosulfuric acid:__________

      (e) Lead(II) chromate: ______________                 (j) Silicon tetrafluoride:____________

B3.   Complete and balance the following equation and write its net ionic equation:

        (a) ___BaCl2(aq) + ___Na2SO4(aq)  __________ + ____________;

        (b) ___AgNO3(aq) + ___Na3PO4(aq)  _________ + ____________

        (c) ___Pb(NO3)2(aq) + ___KI(aq)  _________ + __________

B4.   Balance the following redox reaction in acidic solution using the half-equation method:

        ___Cr2O7(aq) + ___H2O2(aq) + ___H+(aq)  ___Cr3+(aq) + ___H2O(l) + ___O2(g)

B5.   Balance the following redox reaction in basic solution using the half-equation method:

        ___I2(aq) + ___OH-(aq)  ___IO3-(aq) + ___I-(aq) + ___H2O(l)

B6. Magnesium metal and magnesium oxide react with hydrochloric acid according to the following
               Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
                  MgO(s) + 2HCl(aq)  MgCl2(aq) + H2O(l)

      A student obtained a 0.100 g of magnesium strip without polishing it and then reacted it with dilute
      hydrochloric acid in a gas buret (eudiometer). The hydrogen gas produced is collected above water at
      22 oC. (a) If 85.0 mL of H2 gas was collected and the total gas pressure was 728 torr, how many
      moles of H2 were collected? (b) How many grams of pure magnesium reacted with the acid solution?
      (c) What is the percentage (by mass) of magnesium oxide on the strip? (The vapor pressure of water
      at 22oC is 21 torr; R = 0.08206 L.atm/(mol.K))
      (Answer: (a) 0.00336 mol H2; (b) 0.0818 g Mg; (c) 18.2% MgO)

BCC, Fall 2007
Chem 1A Final Review

B7.   (a) Calculate the enthalpy change (Hrxn) for the following reaction:
                 CH3CH2OH(l) + 3 O2(g)  2CO2(g) + 3H2O(g);
        [Hof (kJ/mol): CH3CH2OH(l) = -278; CO2(g) = -393.5;          H2O(g) = -242]
      (b) How many grams of ethyl alcohol (CH3CH2OH) must be burned to provide enough energy to heat
      350.0 g of water from 22.0 oC to 100.0oC? (specific heat of water = 4.184 J/g.oC)
      (Answer: (a) -1235 kJ; (b) 4.26 g)

B8.   If 225 grams of ice at 0oC absorbs 100.0 kJ of heat, what would be the final state: ice and water at 0oC
      or water only? If the final state is water, determine its final temperature. (Answer: water at 26.4oC)
      (Specific heat of water = 4.184 J/g. oC; heat of fusion, Hfus = 6.02 kJ/mol)

B9.   Tungsten crystallizes in a body-centered cubic arrangement and the measurement of each side of the
      unit cell is 321 pm long. Calculate the atomic radius and the density of tungsten. (Atomic mass of
      tungsten = 183.85 u; 1 u = 1.66 x 10-24 g; 1 pm = 10-10 cm)
      (Answer: atomic radius = 139 pm; density = 18.4 g/cm3)

B10. For each of the following substances, predict whether it is more soluble in water or in hexane (C6H14),
     which is a nonpolar solvent)

      (a) CH2Cl2                                          (e) HF

      (b) CH3OH                                           (f) S8

      (c) NaOH                                            (h) H2SO3

      (d) CCl2F2                                          (i) C8H18

B11. (a) If the solubility of KNO3 is 28 g per 100 g of water at 20oC, what is its solubility in 125 g of water
     at the same temperature? (b) What is the percentage (by mass) of KNO3 in a saturated solution of
     KNO3 at 20oC? (c) What is the molality of a saturated solution of KNO3 ?
     (Answer: (a) 35 g; (b) 22% (by mass); (c) 2.8 m)

B12. If concentrated nitric acid solution is 70.0% (by mass) in HNO3 and the density of the solution is 1.48
     g/mL, calculate the molarity and molality of the acid. (Answer: 16.4 M; 37.0 m)

BCC, Fall 2007
Chem 1A Final Review

B13. What are the freezing point and the boiling point, respectively, of a solution that contains 25.0 g of
     NaCl completely dissolved in 150. g of water. (For water: Kf = -1.86oC/m and Kb = 0.512oC/m)
     (Answer: Tf = -10.6oC; Tb = 102.9oC)

B14. Benzene (C6H6) and toluene (C7H8) form an ideal solution. If a mixture is composed of 100.0 g of
     benzene and 100.0 g of toluene, (a) calculate the mole fraction of benzene and toluene, respectively,
     in the mixture. (b) What is the partial pressure of benzene and toluene, respectively, and the total
     vapor pressure above the solution at 25 oC? What is the mole fraction of benzene and toluene,
     respectively, in the vapor at 25oC? The vapor pressure of pure benzene and toluene at 25oC are 95.1
     torr and 28.4 torr, respectively.
     (Answer. XC6H6 = 0.540; XC7H8 = 0.460; PC6H6 = 51.4 torr; PC7H8 = 13.1 torr; PT = 64.5 torr;
     YC6H6 = 0.797; YC7H8 = 0.203)

B15. Radiator fluid is a mixture of water and ethylene glycol (HOCH2CH2OH). The lowering of freezing
     point is proportional to the molal concentration of ethylene glycol in the mixture. (a) How many
     grams of ethylene glycol must be added to 1.50 kg of water so that the solution would freeze at –25.0
       C? (b) At what temperature (in oC) would this solution boil? (Answer: (a) 1250 g; (b) 106.9oC)
     (For water, Kf = -1.86 oC/m, and Kb = 0.512 oC/m)

B16. Lauryl alcohol is obtained from coconut oil and is used to make detergents. A solution of 5.00 g of
     lauryl alcohol in 100. g of cyclohexane freezes at 1.03oC. If the freezing point of pure cyclohexane is
     6.50oC and its Kf = 20.0oC/m, calculate the molar mass of lauryl alcohol. (Answer: 183 g/mol)

B17. (a) How many grams of glucose (mm = 180.2 g/mol) are needed to prepare 500.0 mL of 0.316 M
     glucose solution. (b) Calculate the osmotic pressure of the glucose solution at 25oC. (c) If glucose
     were substituted with NaCl, what concentration of NaCl would yield the same osmotic pressure as the
     glucose solution. (Assume NaCl dissociates completely in aqueous solution.) (R = 0.08206 L.atm/mol.K)
     (Answer: (a) 28.5 g; (b)  = 7.73 atm; (c) 0.158 M)

B18. A 50.0-mL solution containing 2.015 g of poly(vinyl alcohol) (PVA) was found to have an osmotic
     pressure of 105 torr at 25oC. Calculate the molar mass of the PVA sample. (PVA is a nonelectrolyte;
     R = 0.08206 L.atm/K.mol) (Answer: 7.13 x 103 g/mol)


To top