Emf of the cell

EMF OF THE CELL, NUMERICAL PROBLEMS ON CELL EMF

1. Dr. K. RAJENDER REDDY LECTURER IN CHEMISTRY EMAIL:[email protected] 23 April 2020 ELECTRODEPOTENTIAL-KRR 1

2. CONTENTS Electro Motive Force(EMF) Definition Calculation of EMF of the cell EMF of the cell constructed from Cu and Ag Numerical problems 23 April 2020 ELECTRODEPOTENTIAL-KRR 2

3. EMF OF THE CELL Definition : The potential difference between two electrodes of a galvanic cell, which causes flow electrons is called electromotive force(EMF) 23 April 2020 ELECTRODEPOTENTIAL-KRR 3

4. Calculation of EMF of Cell( E cell ) The emf of the cell can be calculated from the elctrode potential values E cell = E cathode -E anode Or E cell = RP of cathode-RP of anode or 23 April 2020 ELECTRODEPOTENTIAL-KRR 4

5. EMF of the cell constructed from Cu and Ag 23 April 2020 ELECTRODEPOTENTIAL-KRR 5 The reading (+0.46 v) of the voltmeter in picture is the EMF of the cell constructed from Cu (anode) and Ag(cathode)

6. Calculation of EMF E cell = E RHS -E LHS Where RHS = Right Hand Side LHS = Left Hand Side E cell = RP of cathode + OP of anode If EMF of the cell is calculated from standard electrode potentials, then it is indicated as E o cell 23 April 2020 ELECTRODEPOTENTIAL-KRR 6 E CELL = E RHS +E LHS

7. NUMERICAL PROBLEMS ON EMF OF THE CELL PROBLEM 1: The SRP of Mg and Cd electrodes are -2.37 V and -0.40 V respectively. Calculate the EMF of the cell Mg/Mg +2 //Cd +2 / Cd . Solution: In this cell Mg is anode and Cd is Cathode. E o cell = E o cathode - E o anode =-0.40 V–(-2.37 V) = + 1.97V 23 April 2020 ELECTRODEPOTENTIAL-KRR 7

8. NUMERICAL PROBLEMS ON EMF OF THE CELL 23 April 2020 ELECTRODEPOTENTIAL-KRR 8 PROBLEM 2: The Zn/Zn +2 electrode potential is +0.76 V and Cu +2 /Cu electrode potential is +0.34V respectively. Calculate the EMF of the cell Zn/Zn +2 // Cu +2 /Cu . Solution: In this cell Zn is anode and Cu is Cathode. E o cell = E o cathode - E o anode = +0.34V –(- 0.76 V) = + 1.1 V

9. NUMERICAL PROBLEMS ON EMF OF THE CELL 23 April 2020 ELECTRODEPOTENTIAL-KRR 9 PROBLEM 3: The Zn/Zn +2 electrode potential is +0.76 V and Ca +2 /Ca electrode potential is -2.87 V . Calculate the EMF of the cell Ca/Ca +2 //Zn +2 /Zn . Solution: In this cell Ca is anode and Zn is Cathode. E o cell = E o cathode - E o anode = -0.76 V –(- 2.87 V) = + 2.10 V

10. NUMERICAL PROBLEMS ON EMF OF THE CELL 23 April 2020 ELECTRODEPOTENTIAL-KRR 10 PROBLEM 4: The SRP of Ni and Cd electrode are -0.25 V and +0.34 V respectively. What is the EMF of the cell constructed from these electrodes. Solution: In this cell Ni is anode and Cd is Cathode. E o cell = E o cathode - E o anode = +0.34V –(- 0.25 V) = + 0.59 V

11. THANK YOU 23 April 2020 ELECTRODEPOTENTIAL-KRR 11