Chm 1316 Honors Freshman Chemistry II Spring 2000
Exam 4 due 9 AM on 1 May 2000

Open Book & Handouts. Solutions are here. Neither Give Nor Receive Help!
  1. What would the units of the rate constant be for a solution reaction that is overall third order?

  2. A silver ion concentration cell starts with [Ag+] of 0.1 M at the anode and 0.3 M at the cathode. Both half cells have the same volume of their respective solutions. What is the cell potential in volts at 25°C when

    1. ...the reaction begins?

    2. ...the reaction ends?

    3. ...the reaction is ½ way to completion?

    RT / F = 59.2 mV at 25°C

  3. Table A5.5 shows the 25°C E° to be -0.35 V for the reduction of PbSO4 to Pb and SO42-(aq). Table 15.4 shows the 25°C Ksp of PbSO4 to be 1.3×10-8. What would E for this reduction be if the only sulfate ion present came from the natural solubility of lead sulfate? [HINT: Balance that reduction reaction equation first.]

  4. When batteries operate, they get warm. That ought to influence their performance. For example, imagine a hydrogen-oxygen fuel cell.

    1. What is the sign of DG°?

    2. Therefore, what is the sign of E°?

    3. What is the sign of DS°?

    4. Therefore, what is the sign of dG/dT assuming temperature independent DH° and DS°? [Remember the definition of G.]

    5. Hence, what is the sign of dE/dT? Does the fuel cell perform better cool or warm?

    6. Extra Credit: Using Appendix Four, calculate the change in E for the fuel cell with a 10°C temperature rise, assuming fixed DH° and DS°.

  5. For some reaction, the amount of reactant, A, remaining after time, t, is found to be:

    Time (s)0.005.0010.00
    [A] (M)0.010000.005700.00325

    1. What is the order of the reaction in A?

    2. What is the reaction's rate constant?

    3. What is its (initial) half-life?

  6. The destruction of ozone by NO (to make O2 and NO2) proceeds both at sea level (in smog) where the temperature is 25°C and in the stratosphere where the temperature is -40°C. Eact for this reaction is 11.4 kJ/mol.

    1. If the concentrations of these reactants were the same in both places, what would the ratio of the reaction rates (stratosphere vs. sea level) be?

    2. But if the mole fractions of NO and ozone found at sea level were transported to the stratosphere, where the pressure is only 0.01 that of sea level, their concentrations would definitely not be the same as at sea level. Given that this reaction is elementary, what would be the ratio of stratospheric to sea level rate of reaction for O3 + NO?

  7. Molecular chlorine is made by the electrolysis of seawater. If the cell housing the reaction runs at 5 amps, how long does it take to produce each liter of Cl2 at STP?

  8. The overall reaction

    A + 2 B ---> P

    is imagined to go by the following mechanism:

    A + B ---> C       k1 (slow)
    C + B ---> P       k2 (fast)

    What is the rate expression for the appearance of product, P?

  9. Which metals would an oxygen-free, aqueous solution of copper(I) acetate corrode?

    1. lead
    2. manganese
    3. mercury
    4. silver
    5. tin

  10. The following rates of reactions are found for varying initial concentrations of species A, B, and C:

    [A] (M)[B] (M) [C] (M)Rate (M/s)
    0.10.10.10.36
    0.20.10.21.44
    0.10.20.20.72
    0.20.20.22.88

    1. What is the rate expression that is consistent with this data?

    2. What is the value of the rate constant (and its appropriate units)?

Comments or QUESTIONS to Chris Parr Return to CHM 1316 HomePage Last modified 1 May 2000.