A voltaic cell is assembled at 298K with Fe (s) and Fe(NO 3 ) 2 (aq) in one comp

Question

A voltaic cell is assembled at 298K with Fe (s) and Fe(NO3)2(aq) in one compartment and Au (s) and Au(NO3)3(aq) in the other. An external wire connects the two electrodes, and a salt bridge containing KNO3 connects the two solutions,

Fe2+(aq) + 2 e à Fe (s) E° = –0.44 V

Au 3+(aq) + 3 e à Au (s) E° = 1.50 V

#7. What is the standard cell potential for the above electrochemical cell?

– 1.94 V

1.94 V

1.06 V

– 1.06 V

3.62 V

#8. What is the value of G° for the above electrochemical cell?

–1123 kJ

–562 kJ

–374 kJ

1123 kJ

613 kJ

#9. Which of the following statements concerning the above electrochemical cell is

       incorrect?

As the reaction proceeds, the value of Ecell decreases.

As the reaction proceeds, the value of K° remains constant.

As the reaction proceeds, the value of G° approaches zero.

As the reaction proceeds, the mass of the anode electrode decreases.

All of the above statements are correct.

Explanation / Answer

Fe2+(aq) + 2 e- -----> Fe (s) E° = -0.44 V

Au 3+(aq) + 3 e ------> Au (s) E° = 1.50 V

SInce the Eo for Fe is negative it needs to be reversed

Fe (s)   -----> Fe2+(aq) + 2 e- E° = +0.44 V

SO total Eo for the cell is +0.44V + 1.50 V = 1.94 V

So the right answer is

What is the standard cell potential for the above electrochemical cell?

1.94 V

#8. What is the value of G° for the above electrochemical cell?

The balanced equation will be

3Fe (s) + 2Au 3+(aq) ------> 2Au (s) + 3Fe2+(aq) so 6 electrons are exchanged for this

so delta Go = -nFEo

delta Go = - 6 x 96485 x 1.94

delta Go = 1123 kJ

So right answer is 1123kJ

As the reaction proceeds, the value of Ecell decreases. - this is correct because as the concentration of ions change th Ecell will decrease

As the reaction proceeds, the value of K° remains constant. - K is rate constant and it remains constant throughout

As the reaction proceeds, the value of G° approaches zero. - this is also correct as the Ecell decreases the Go will decrease

As the reaction proceeds, the mass of the anode electrode decreases. - This is correct since the anode is where oxidation happens so the metal gets converted to ions and so mass decreases

So the right answer is

All of the above statements are correct.

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