Many of the basic concepts of electrochemistry and potentiometry can be illustra

Question

Many of the basic concepts of electrochemistry and potentiometry can be illustrated with a “battery in a beaker” set up as shown here. Suppose that one of the cells shown here consists of a strip of lead setting in a solution of Pb2+ (aq) while the other beaker gold in an Au3+ (aq) solution.

A. The following reactions and potentials are standard for the two metal ions: Au3+ (aq) + 3e- ! Au (s) Eo = +1.42 V Pb2+ (aq) + 2e- ! Pb (s) Eo = - 0.13 V Label the cathode (right side) with the proper metal symbol on the metal strip in the diagram.

(B) What is the Eo value for the cell?

(C) Assume the salt bridge shown here contained dissolved KNO3. Add another arrow on the diagram, near the salt bridge to indicate the direction of K+ migration through the salt bridge.

(D) Write out the proper balanced redox equation (using only the metals and ions).

(E) Of the following which is the reducing agent? Pb; Pb2+; Al; Al3+

(F) Write out the “line diagram” that represents this cell:

3 Many of the basic concepts of electrochemistry and potentiometry can be illustrated with a "battery in a beaker" set up as shown here. Suppose that one of the te cells shown here consists of a strip of lead setting in a solution of Pb2 (a) while the other beaker gold in an Au' (ag) solution. (A) The following reactions and potentials are standard for the two metal ions Au3+ (aq) + 3e- Au (s) E +1.42 V Pb2+ (aq) + 2e- Pb (s) E" = _ 0.13 V Label the cathode (right side) with the proper metal symbol on the metal strip in the diagram (B) What is the E value for the cell? (C) Assume the salt bridge shown here contained dissolved KNO3. Add another arrow on the diagram, near the salt bridge to indicate the direction of K' migration through the salt bridge (D) Write out the proper balanced redox equation (using only the metals and ions) (E) Of the following which is the reducing agent? Pb; Pb*; Al; Al* (F) Write out the "line diagram" that represents this cell (G) What is the value of G° for the redox reaction?

Explanation / Answer

I'll answer A, B E and G. I have a doubt in D, and C and F try to answer yourself with the indications here:

A) The cathode is the one that is reducting, and in this case, the cathode would have the higher reduction potencial. So in this case, the gold is reducting and lead is oxidating.

B) 3* (Pb2+ + 2e- --------- Pb ) = 3Pb2+ + 6e- = 3Pb

(Au = Au3+ + 3e-) = 2Au = 2Au3+ + 6e-

3Pb2+ + 2Au = 3Pb + 2Au3+

Eº = (2*1.42) + (3*0.13) = 3.23 v

Eº = 1.42 + 0.13 = 1.55 V

E) As I stated before, is lead is oxidating, therefore, is the best reductor agent (Pb2+)

G) To calculate that we need the following expression: G = -nFE

Gº = -2 * 96485 * 1.55

Gº = -6*3.23*96485

Gº = -1869.87 kJ/mol

Hope this helps.

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