Last modified: Mon 10/21/2013 10:43:45 pm
BCE

Do not press the RETURN or ENTER key while you are answering these questions. Your browser will interpret either the same as clicking on the Submit key.

Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.

First Name:

Last Name:

Laboratory Section:

For this BCE we will use this short version of the Standard Reduction Potential Table. You might want to print the table out before beginning the BCE.

Answer the following questions using the SRP Table.

1. Identify the species (name and/or formula) from the table above that is the most likely to be oxidized.

2. Identify the species (name and/or formula) from the table above that is the most likely to be reduced.

We can use the Standard Reduction Potential Table to calculate the E° for a reaction. For example, we measured E° for a reaction Zn(s) + Cu2+(aq) ----> Cu(s) + Zn2+(aq). We can calculate the E° the following way;

i) separate the reaction into its corresponding half-reactions;

ii) The oxidation half-reaction occurs at the anode and the reduction half-reaction occurs at the cathode:

iii) look up the E° for the half-reactions in the Standard Reduction Potential Table;

iv) calculate E° using the relationship E° = E°cathode - E°anode

So for the reaction Zn(s) + Cu2+(aq) ----> Cu(s) + Zn2+(aq)

the half-reactions are

Zn(s)----> Zn2+(aq) + 2e- (oxidation at the anode)

2e- + Cu2+(aq) ----> Cu(s) (reduction at the cathode)

From the SRP Table the E° for the half-reactions are

Half-reaction

E° (volts)

2e- + Cu2+(aq) ----> Cu(s)

+0.34

2e- + Zn2+(aq) ----> Zn(s)

-0.76

We determine E° for the reaction by using the equation E° = E°cathode - E°anode = +0.34 v - (-0.76 v) = +1.10 v (NOTE: When using this relationship both half-reaction are represented as reduction half-reactions)

So E° = +1.10 v

3. Using the Table of Standard Reduction Potentials determine whether each of the following reactions has a positive E° (standard cell potential) or a negative E°.

a) 2Cl-(aq) + Cu2+(aq) ----> Cl2(g) + Cu(s) : E° = volts

b) Mg(s) + Ca2+(aq) ----> Ca(s) + Mg2+(aq) : E° = volts

c) H2O2(aq) + 2H+(aq) + 2Br-(aq) ----> 2H2O(l) + Br2(g): E° = volts

4. Will Pb(s) reduce Ag+(aq)? (Y/N)

Explain

5. Will 1 M HNO3 oxidized Cu(s)? (Y/N)

Explain

6. Will 1 M HCl oxidized Cu(s)? (Y/N)

Explain

7. Identify a reagent that will oxidize Zn(s) but will not oxidize Pb(s).

8. Using half-reactions from the table of Standard Reduction Potentials predict the products of the following reaction;

Pb(s) + Cr2O72-(aq) + H+(aq) ---->

9. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

10. If there is one question you would like to have answered in lecture, what would that question be?