Name:______
College Now Chemistry
Chapter 17-18 Test
[Due: Tuesday, June 10th, 2014]
1. The element fluorine, F2 was first produced in 1886 by electrolysis of HF. Chemical syntheses of F2 did not happen until 1986 when Karl O. Christe successfully prepared F2 by the following reaction
K2MnF6 (s) + 2 SbF5 (l) 2 KSbF6 (s) + MnF3 (s) + ½ F2 (g)
a. Assign oxidation numbers to each compound and determine the number of electrons involved in this process.
b. Using the following ∆Hfo values, calculate ∆Hfor the reaction
∆HfoSbF5(l) = -1324 kJ/mol / ∆HfoK2MnF6(s) = -2435 kJ/mol∆HfoMnF3(s) = -1579 kJ/mol / ∆HfoKSbF6(s) = -2080 kJ/mol
c. If we assume that ∆S is relatively small, such that ∆G ≈∆H, estimate Eo for this reaction
d. If ∆S for the reaction is greater than zero, is our value for Eo in part c too high or too low? Why?
e. The electrochemical synthesis of F2 is described by the electrolytic cell reaction
2 KHF2 (l) 2 KF (l) + H2 (g) + F2(g)
Assign oxidation numbers and determine the number of electrons involved in this process.
2. A voltaic cell with an aqueous electrolyte is based on the reaction between Pb2+ (aq) and Zn(s), producing Pb (s) and Zn2+ (aq).
a. Write half-reactions for the anode and the cathode.
b. Write a balanced cell reaction.
c. Diagram the cell (draw a picture of the cell).
d. Calculate Eocell for this voltaic cell, using reduction potentials in the appendix of your textbook.
e. Write the description of the cell in line notation form.
3. A NiMH (nickel-metal-hydride) battery containing 4.10 g of NiO(OH) was 50% discharged when it was connected to a charger with an output of 2.00 A at 1.3 V. How long does it take to recharge this battery?
The overall cell reaction (in basic solution) for a typical NiMH battery is
MH (s) + NiO(OH) (s) M(s) + Ni(OH)2 (s)
where M stands for a transition metal (or alloy) that forms a hydride.
4. Use the data from the appendix in your textbook to calculate ∆Go for each of the following reactions. Assuming that the values of ∆Ho and ∆So do not change appreciably with temperature, is each reaction spontaneous at 355 K? [show work]
a. N2(g) + O2(g) 2 NO(g)
b. 2 NO(g) + O2(g) 2 NO2 (g)
c. NO (g) + ½ O2 (g) NO2 (g)
d. 2 NO2 (g) N2O4 (g)
5. Under the appropriate conditions, NO forms N2O and NO2:
3 NO (g) N2O (g) + NO2 (g)
Use the values for ∆Go for the following reactions to calculate the value of Kp for the above reaction at 500 oC.
2 NO (g) + O2 (g) 2 NO2 (g) / ∆Go = -69.7 kJ2 N2O (g) 2 NO (g) + N2 (g) / ∆Go = -33.8 kJ
N2 (g) + O2 (g) 2 NO (g) / ∆Go = 173.2 kJ
6. Consider the following situation as you answer the questions a-e. [1000 pts*]
For reasons we don’t need to get into here, Marcus McGovern, while visiting the zoo falls into the chimpanzee exhibit. He finds himself confronted by a riled-up male chimpanzee.
a. Estimate the Governor’s chances of survival. (include equations or graphs if necessary)
b. If Marcus were to battle the chimpanzee 50 (fifty) times, how many of these battles do you expect that he would win?
c. Are you Marcus McGovern?
d. Do you suspect that you have a man-crush on Marcus McGovern?
(Charlie, Solan, Liam, Karl & Clay- don’t feel compelled to answer this, we know)
e. What do you think the chances are that Mr. Whalley is actually going to award points for your answers to the above question? [hint: it is 0.0%]
- …you’re not seriously considering this. Right?
Whalley\CN Chemistry
Ch. 17-18 Take-Home\Spring 2014 page 1