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    UC Davis CHE 2B: General Chemistry 
    Spring 2012: Larsen

    Chem 2A        Chem 2B        Chem 2C

    Homework Problems
    Homework Solutions
    Grading on a Curve
    Unit I: Thermochemistry            Unit II: States of Matter           Unit III: Acids and Bases         Unit IV: Chemical Equilibria

    The key will NOT be given, but after each problem there is a link to an answer and/or discussion site. Use this page to post questions about the problems for your fellow students to answer

    Problem 1

    True/False questions (concepts).

    1. Work is a state function
    2. A Lewis acid is a proton donor
    3. Solubility is independent of temperature
    4. Thermal energy is the total energy available in a system
    5. London dispersion forces increase with the size of the molecule
    6. In the titration of a strong acid with a strong base pH = 7 at the equivalence point (or stoichiometric point)
    7. The buffer capacity depends on pKa of the acid
    8. Surface tension decreases with temperature
    9. The equilibrium constant is formally defined in terms of activities, not concentration
    10. Temperature is a state function
    11. Adding product to a chemical reaction at equilibrium will shift the reaction toward more reactants
    12. At equilibrium Gr=0
    13. For a process to be spontaneous the entropy of the system must increase
    14. Energy can neither be created nor destroyed
    15. The heat capacity is independent of the size of the system
    16. The specific heat capacity is independent of the size of the system
    17. Free energy is the total energy stored in a system
    18. A saturated solution is at equilibrium
    19. The vapor pressure is an example of an equilibrium constant
    20. qV (the heat at constant volume) is an example of a path function
    21. The entropy of a perfect crystal at room temperature is zero
    22. CO (g) has a larger heat capacity than CO2 (g)
    23. Ethanol (CH3CH2OH) has a higher boiling point than propane (CH3CH2CH3)
    24. pH increases during the titration of a weak acid with a strong base
    25. A buffer solution contains close to equal concentrations of a weak acid and its conjugate base
    26. If a reaction involving gases is at equilibrium initially, increasing pressure by adding an inert gas will drive the reaction to the side with the lower number of gas.

    Problem 2

    40 mL of acetic acid is titrated with a 1.342 M solution of NaOH. The stoichiometric point (or equivalence point) is observed after 3.02 mL of base is added

    (Look up any constants you need in the book, the tables you need will be available at the exam)

    1. What is the concentration of the original acetic acid solution?
    2. What is pH after 1 mL of base has been added?
    3. How many mL of base would you need to add to make a buffer solution with pH = 4.8?

    Problem 3

    Given that ethanol boils at 78.4 C at 1 atm and the heat of vaporization is 38.6 kJ/mol, what is the entropy of vaporization?

    Problem 4

    What is the ionic strength of a 0.100 M solution of MgSO4?

    Problem 5

    How many grams of sodium nitrite (NaNO2) must be added to 150 mL of a 0.20 M nitrous acid (HNO2) to make a buffer solution of pH=4.0?

    Problem 6

    Ksp=1.8x10-10 for AgCl. Assuming that all activity coefficients are 1, what is the solubility of AgCl in

    1. pure water?
    2. 0.010 M aqueous solution of NaCl?
    3. 0.001 M aqueous solution of NaBr?

    Problem 7

    Given that \(\Delta{H_r}=92.22 kJ\) and \(\Delta{S_r}\)=198.75 J K-1 for the reaction

    \[2 NH_3 (g) \rightarrow 3H_2 (g) + N_2 (g)\]

    estimate the temperature at which the reaction is spontaneous. Assume that \(\Delta{H_r}\) and \(\Delta{S_r}\) are temperature independent.

    Question 1

    What is the mass of 1.2 x 10-3 moles of CsCl?

    Question 2

    2.3 moles of \(H_2\) gas and 1.3 moles of \(O_2\) (g) reacts to form \(H_2O\) according to the reaction:

    \[ 2 H_2 (g) + O_2 (g) \rightarrow 2 H_2O (g)\]

    The reaction goes to completion. How many moles of H2O is formed?