Q68 of 136 Page 43

What is the relationship between Gibbs free energy of the cell reaction in a galvanic cell and the emf of the cell? When will the maximum work be obtained from a galvanic cell?

• The relationship between Gibbs free energy of the cell reaction in a galvanic cell and the emf of the cell:


ΔrGcell = -nFEcell


Where, ΔrGcell = Gibbs free energy of the reaction.


F= Faraday constant


Ecell = Emf of the cell


n= Number of moles of electron transferred in the radox reaction.


• At standard condition,


When, concentration of all reacting species is unity, T= 298 K


Ecell =


Or, ΔG° = -nF


• The maximum work can be obtained from a galvanic cell when the charge is passed reversibly.


• The reversible work done by the galvanic cell is written as,


ΔrGcell = -nFEcell


More from this chapter

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66

Consider the Fig. 3.2 and answer the following questions.


(i) Cell ‘A’ has ECell = 2V and Cell ‘B’ has ECell = 1.1V which of the two cells ‘A’ or ‘B’ will act as an electrolytic cell. Which electrode reactions will occur in this cell?


(ii) If cell ‘A’ has ECell = 0.5V and cell ‘B’ has ECell = 1.1V then what will be the reactions at anode and cathode?

 67

Consider Fig. 3.2 and answer the questions (i) to (vi) given below.

(i) Redraw the diagram to show the direction of electron flow.


(ii) Is silver plate the anode or cathode?


(iii) What will happen if salt bridge is removed?


(iv) When will the cell stop functioning?


(v) How will concentration of Zn2+ ions and Ag+ ions be affected when the cell functions?


(vi) How will the concentration of Zn2+ ions and Ag+ ions be affected after the cell becomes ‘dead’?


 66

Consider the Fig. 3.2 and answer the following questions.


(i) Cell ‘A’ has ECell = 2V and Cell ‘B’ has ECell = 1.1V which of the two cells ‘A’ or ‘B’ will act as an electrolytic cell. Which electrode reactions will occur in this cell?


(ii) If cell ‘A’ has ECell = 0.5V and cell ‘B’ has ECell = 1.1V then what will be the reactions at anode and cathode?


 67

Consider Fig. 3.2 and answer the questions (i) to (vi) given below.

(i) Redraw the diagram to show the direction of electron flow.


(ii) Is silver plate the anode or cathode?


(iii) What will happen if salt bridge is removed?


(iv) When will the cell stop functioning?


(v) How will concentration of Zn2+ ions and Ag+ ions be affected when the cell functions?


(vi) How will the concentration of Zn2+ ions and Ag+ ions be affected after the cell becomes ‘dead’?