Last modified: Wed 12/31/1969 06:00:00 pm
ACA

Oklahoma State University

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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 ACA we will use this short version of the Standard Reduction Potential Table.

Answer the following questions using the SRP Table.

1a. Calculate the standard cell potential for the reaction

3Mg(s) + 2Al3+(aq) ----> 3Mg2+(aq) + 2Al(s)

Eo = volts

b) What is the value of K for the reaction in Question 1a.

(Go = -nFEo where F = 96,500 J volt-1

and Go = -RT ln K where R = 8.314 J mol-1 K-1

so Eo = RT/nF ln K or Eo = 0.0257/n ln K

n is the number of electrons transferred in the balanced chemical equation)

K =

c) For the E˚ calculated in 1a what are the standard concentrations for [Al3+] and [Mg2+]?

[Al3+] = [Mg2+] = M

2. Given that Ecell = Eocell- (0.0257/n) ln Q
complete the missing cells in the table below

Experiment

[Al3+]

[Mg2+]

Eocell (volts)

Ecell (volts)

Q ([Mg2+]3/([Al3+]2)

1

1.0 M

1.0 M

+0.70

+0.70

2

0.5 M

1.75 M

+0.70

21.4

3

0.050 M

+0.70

+0.66

4

0.0010 M

2.499 M

+0.70

+0.63

1.56 x 107

5

1.0 x 10-10

2.500 M

+0.70

+0.50

1.56 x 1021

3a. What happens to the value of Q as the reaction proceeds from left to right?

b. What happens to the cell potential as the reaction proceeds from left to right?

c. What value is Ecell approaching as the reaction proceeds from left to right?

volts

d. What value is Q approaching as the reaction proceeds from left to right?

4a. When Q is greater than 1 what is the sign of ln Q?

(positive or negative)


b. When Q is less than 1 what is the sign of ln Q?

(positive or negative)

c. When Q is greater than 1 is  Ecell  greater than, less than or equal to Eocell ?



d. When Q is less than 1 is  Ecell  greater than, less than or equal to Eocell ?

 

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

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