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    (Chem 16) Long Exam 2 Reviewer A

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    Roland Franco

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    (Chem 16) Long Exam 2 Reviewer A

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    Roland Franco
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    [CHEM 16] LONG EXAM 2 REVIEWER A

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    (Chem 16) Long Exam 2 Reviewer A

    Uploaded by

    Roland Franco

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    © All Rights Reserved
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    of 6

    1. How many Mg2+ ions are present in 0.500 g of magnesium phosphate?

    A. 1.15 x 1021 ions


    B. 2.29 x 1021 ions
    C. 3.44 x 1021 ions
    D. 6.02 x 1023 ions

    2. How many moles of He are present in a 2.00 L cylinder containing He gas (ρ = 0.179
    g/L)?

    A. 0.0224 moles
    B. 0.0895 moles
    C. 0.358 moles
    D. 1.432 moles

    3. How many grams of Ca are present in 20.0 g of CaO?


    A. 16.0 g
    B. 14.3 g
    C. 10.0 g
    D. 5.71 g

    4. A 4.50-g sample of Na2SO4•xH2O was heated until all of the water of hydration is lost. The resulting
    anhydrous compound weighs 1.98 g. What is the value of x?
    A. Na2SO4•4H2O
    B. Na2SO4•6H2O
    C. Na2SO4•8H2O
    D. Na2SO4•10H2O

    5. A 6.00% (w/w) solution of HCl has a density of 1.0279 g/mL. What is the molarity of the
    solution?

    A. 0.169 M
    B. 1.69 M
    C. 0.184 M
    D. 1.84 M

    6. Which of the following reactions is incorrectly paired with its type of aqueous
    reaction?

    A. Precipitation: 2Na3PO4 + 3MgCl2 ® 6NaCl + Mg3(PO4)2


    B. Neutralization: H2CO3 + 2KOH ® K2CO3 + 2H2O
    C. Redox: CuSO4 + Pb(NO3)2 ® Cu(NO3)2 + PbSO4
    D. Precipitation: AlBr3 + 3NaOH ® 3NaBr + Al(OH)3
    7. 10.0 mL of 1.00 M KCl and 25.0 mL of 0.50 M MgCl2 were mixed together. What is the concentration
    of chloride ions in the final solution?
    A. 0.0225 M
    B. 0.643 M
    C. 0.900 M
    D. 1.00 M

    For numbers 8 to 10, refer to the following equation:

    KO2 + CO2 ® K2CO3 + O2

    8. What is the coefficient of O2 in the balanced equation?


    A. 1
    B. 2
    C. 3
    D. 4

    9. How many moles of O2 are produced by the reaction of 156 g CO2 with excess KO2?
    A. 3.55 moles
    B. 5.32 moles
    C. 2.36 moles
    D. 1.77 moles

    10. How many grams of KO2 are consumed per 100.0 g of CO2?
    A. 2.28 g
    B. 162 g
    C. 4.55 g
    D. 323 g

    11. For the reaction N2(g) + H2(g) → N2H4(l), if the percent yield in an experiment was found to be 82.5%, what
    is the actual mass of hydrazine (N2H4) produced when 23.11 g of nitrogen reacts with 3.55 g of
    hydrogen?

    A. 32.0 g
    B. 21.8 g
    C. 26.7 g
    D. 26.4 g

    12. A 15.0 mL aliquot of 0.25 M NaOH was mixed with 35.0 mL of water. If the individual volumes are
    additive, what is the final concentration of the dilute solution?
    A. 0.075 M
    B. 0.107 M
    C. 0.175 M
    D. 0.350 M
    13. Which of the following represents a closed system?
    A. Hot coffee in a mug
    B. Helium gas in a balloon
    C. Water in a bomb calorimeter
    D. Dry ice in a thermos

    14. A balloon containing 1.0 mole of helium gas (c = 5.19 J/g°C) at 1 atm was heated from 25.0°C to
    50.0°C. As a result, it expanded by 2.5 L. What is the change in internal energy of the surroundings?
    A. +266 J
    B. -266 J
    C. +519 J
    D. -519 J

    15. Given one mole of each metal, which one requires the most energy to increase its temperature
    by 1 °C?
    A. Aluminum (c = 0.900 J/g.°C)
    B. Iron (c = 0.444 J/g.°C)
    C. Silver (c = 0.240 J/g.°C)
    D. Lead (c = 0.160 J/g.°C)

    16. The heat of solution of potassium acetate in water is -15.3 kJ/mol KC2H3O2. If 0.136 mol KC2H3O2 is
    dissolved in 525 mL water that is initially at 25.1 °C, what will be the final solution temperature?
    Assume that the solution has a density of 1.00 g/mL and its specific heat is 4.184 J/g-°C.
    A. 32.1 °C
    B. 26.0 °C
    C. 24.2 °C
    D. 18.1 °C

    17. A 1.250 g sample of xylose (C5H10O5) was combusted in a bomb calorimeter, resulting in a temperature
    increase from 24.37 °C to 28.29 °C. If the heat capacity of the calorimeter is 4.728 kJ/°C, what is the
    heat of combustion of xylose?
    A. –14.8 kJ/mol
    B. – 22.3 kJ/mol
    C. – 1480 kJ/mol
    D. – 2230 kJ/mol

    18. The standard enthalpy of formation of NH3(g) is -46.11 kJ/mol NH3. What is the ΔHofor the following
    reaction?

    2/3NH3(g) ® 1/3N2(g) + H2(g)


    A. -46.11 kJ
    B. 46.11 kJ
    C. -30.74 kJ
    D. 30.74 kJ
    19. Which of the following reactions will result to a decrease in entropy of
    the system? A. Mg(s) + 2HCl(aq) ® MgCl2(aq) + H2(g)
    B. H2CO3(aq) ® H2O(l) + CO2(g)
    C. 2KClO3(s) ® 2KCl(s) + 3O2(g)
    D. N2(g) + 3H2(g) ® 2NH3(g)

    20. Which of the following reactions will be spontaneous at all temperatures?


    A. CaCO3(s) ® CaO(s) + CO2(g) ΔHo = +178.32 kJ/mol
    B. H2O(g) ® H2O(l) ΔHo = -40.67 kJ/mol
    C. CH4(g) + 2O2(g) ® CO2(g) + 2H2O(l) ΔHo = -890.30 kJ/mol
    D. C6H12O6(s) ® 2C2H5OH(l) + 2CO2(g) ΔHo = -72.00 kJ/mol

    21. Which of the following processes/reactions has a ΔG value not equal to zero?
    A. Condensation of water vapor to liquid at 100 °C
    B. Melting of ice to liquid water at 298 K
    C. Freezing of liquid water to ice at 273 K
    D. Boiling of water to water vapor at 373 K

    22. Octane (C8H18) undergoes combustion according to the following thermochemical equation:
    2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ΔH0rxn = -11 020 kJ/mol
    Given that ΔH0f [CO2(g)] = -393.5 kJ/mol and ΔH0f [H2O(l)] = -285.8 kJ/mol, calculate the enthalpy of
    formation of octane.

    A. -210 kJ/mol
    B. -11 230 kJ/mol
    C. 22 040 kJ/mol
    D. -420 kJ/mol

    23. Use Hess’s Law to determine ΔHofor the reaction

    C3H4(g) + 2H2(g) ® C3H8(g)

    (1) H2(g) + ½ O2(g) ® H2O(l) ΔHo = -285.8 kJ


    (2) C3H4(g) + 4O2(g) ® 3CO2(g) + 2H2O(l) ΔHo = -1937 kJ
    (3) C3H8(g) + 5O2(g) ® 3CO2(g) + 4H2O(l) ΔHo = -2219.1 kJ

    A. -3.7 kJ
    B. -289.5 kJ
    C. -853.7 kJ
    D. -4728 kJ
    24. Using bond enthalpies provided below, estimate the ΔH0comb (enthalpy of combustion) of 1 mole of
    propane, C3H8. Use the bond energy values (in kJ/mol):

    C–H = 413, C–C = 347, C=C = 614, O=O = 498, C–O = 358, C=O = 805, H–O = 464

    A. 2 786 kJ
    B. 3 466 kJ
    C. –2 054 kJ
    D. –680 kJ

    25. HI has a normal boiling point of –35.4 °C, and its ΔHvap is 21.16 kJ/mol. Calculate the entropy of
    vaporization (ΔSvap).

    A. 598 J/mol K
    B. 68.6 J/mol K
    C. 89.0 J/mol K
    D. 0.068 J/mol K

    II. PROBLEM SOLVING. Show your solutions and box your final answer.

    1. Dimethylhydrazine is a carbon-hydrogen-nitrogen compound used in rocket fuels. When burned


    completely, a 0.505-g sample yields 0.741 g CO2 and 0.605 g H2O. The nitrogen content of a 0.486-g
    sample is converted to 0.226 g N2. What is the empirical formula of dimethylhydrazine? (7 points)

    2. Ammonia can be generated by heating together the solids NH4Cl and Ca(OH)2. This reaction also
    forms CaCl2 and H2O as side products. Consider a mixture containing 33.0 g each of NH4Cl and
    Ca(OH)2 that is heated to generate ammonia.
    A. Write down the balanced chemical equation. (2 points)
    B. Which of the two reactants is limiting? Show your solution. (3 points)
    C. How many grams of NH3 will form? (2 points)
    D. If the actual mass of ammonia produced was 8.5 g, what is the percent yield of the
    reaction? (2 points)
    E. How many moles of the excess reactant will be left after the reaction? (2 points)
    3. Given the following data at 298 K:

    ΔHfo(kJ mol-1) ΔGfo(kJ mol-1)

    NH3(g) -46.11 -16.48

    HCl(g) -92.31 -95.30

    NH4Cl(s) -314.4 -202.9

    A. Determine ΔSo for the reaction NH3(g) + HCl(g) ® NH4Cl(s). (5 points)


    B. Is the reaction spontaneous or not? Justify your answer. (2 points)
    C. At which temperature will the reaction be in equilibrium? (2 points)

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