Electrochemistry Numericals Assignment

Electrochemistry

Galvanic cell, EMF, Nernst Equation

Q1. Given the standard electrode potentials: K⁺/K=-2.93V, Ag⁺/Ag=0.80V, Hg²⁺/Hg=0.79V, Mg²⁺/Mg=-2.37V, Cr²⁺/Cr=-0.74V. Arrange them in their increasing order of reducing power.

Q2. Depict the galvanic cell in which the reaction: 2Zn + 2Ag⁺    →   Zn²⁺ + 2Ag takes place. Further show: (i) which of the electrode is negatively charged, (ii) the carriers of the current in the cell, (iii) Individual reaction at each electrode.

Q3. Write the Nernst equation and the EMF of the following cells:

(i) Mg(s)|Mg²⁺(0.001M)||Cu²⁺(0.0001M)|Cu(s)

(ii) Fe(s)|Fe²⁺(0.001M)||H⁺ (1M)|H₂(g)(1bar)|Pt(s)

(iii) Pt(s)|Br₂(l)|Br^-(0.01M)|| H⁺ (0.03M)|H₂(g)(1bar)|Pt(s)

Given E^o Mg²⁺|Mg =-2.37V, E^o Cu²⁺|Cu =+0.34V, E^o Fe²⁺|Fe =-0.44V, E⁰ Br₂|Br^- =1.08V.

Q4. Predict if the following reactions are feasible: (i) Fe3+(aq) and I-(aq)  (ii) Ag+(aq) and Cu    (iii) Br2(aq) and Fe2+(aq). Given: E^o Fe²⁺|Fe³⁺ =-0.774V,  E⁰ Br₂|Br^- =1.09V,  E^o Ag⁺/Ag =0.80V,  E⁰  I₂|I^- =0.541V.

Q5. How would you determine the standard electrode potential of Mg²⁺|Mg?

Q6. Can you store CuSO₄ solution in a zinc pot, E^o Zn²⁺|Zn =-0.76V, E^o Cu²⁺|Cu =+0.34V.

Q7. Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

Q8. E^o values : Zn(OH)₂|Zn =-1.245V, Mg(OH)₂|Mg =-2.69V, Fe(OH)₂|Fe =-0.877V, Fe(OH)₃|Fe =-2.3V

(i) Which is the strongest reducing agent?

(ii) Which reducing agent could reduce Zn(OH)₂ to Zn?

(iii) Which reducing agent could reduce Fe(OH)₂ to Fe?

Q9. A zinc rod is dipped in 0.1M solution of ZnSO₄. The salt is 95% dissociated at this dilution at 298K. Calculate the electrode potential. E^o Zn²⁺|Zn =+0.76V.

Q10. Represent the cell in which the following reaction takes place: 2Mg + 2Ag⁺(0.0001M)  → Mg²⁺(0.130V) + 2Ag. Calculate its Ecell if E^ocell = 3.17V.

Q11. Calculate the standard free energy change and maximum work obtainable for the reaction occurring in Daniel cell; Zn + Cu²⁺   →  Zn²⁺ + Cu and also calculate the equilibrium constant for the reaction. Given: E^o Zn²⁺|Zn =+0.76V. E^o Cu²⁺|Cu =+0.34V

Q12. Estimate the minimum potential difference needed to reduce Al₂O₃ at 500^oC. The standard energy change for the reaction is 960KJ.       2/3 Al₂O₃  →  4/3Al + O₂

Q13. The cell in which the following reaction occurs:  2Fe³⁺ + 2I^-  →  2Fe²⁺ + I₂ has E^ocell = 0.236V Calculate gibbs free energy change and equilibrium constant of the cell reaction.

Q14.  0.05M NaOH solution offered a resistance of 31.6 Ω in a conductivity cell at 298K. If the cell constant of the cell is 0.367 cm^-1, calculate molar conductivity of the solution.                              [232 Ω^-1cm²mol^-1]

Q15. The resistance of semimolar solution of an electrolyte enclosed between two platinum electrodes 1.5 cm apart and having an area of 2 cm² was found to be 30 Ω. Calculate the molar conductance of the solution. [50 Ω^-1cm²mol^-1]

Q16. The specific conductance of a 0.01M solution of acetic acid at 298k is 1.65 X 10^-4 Ω^-1 cm^-1. Calculate: (i) molar conductance of the solution, (ii) degree of dissociation of acetic acid, (iii) dissociation constant. [Given: Λ⁰(H⁺) =349.1 and Λ⁰(CH₃COO^-) =40.9 Ω^-1cm²mol^-1]

Q17. The molar conductance at infinite dilution for NH₄Cl, NaOH and NaCl are 129.8, 217.4 and 108 Ω^-1cm²mol^-1 respectively. If molar conductance of 0.01M solution of NH₄OH is 9.33 Ω^-1cm²mol^-1. Calculate (i) molar conductance at infinite dilution, (ii) degree of dissociation of NH₄OH.

Q18. The Λ⁰ values of KNO₃ and LiNO₃ are 145 and 110.1 Ω^-1cm²mol^-1 respectively. The Λ⁰ value for K⁺ ion is 73.5 Ω^-1cm²mol^-1.Calculate Λ⁰(Li⁺). [38.6 Ω^-1cm²mol^-1]

Q19. Calculate the number of coulombs required to deposit 6.75g of Al from AlCl₃.

Q20. An aqueous solution of an unknown salt of Palladium is electrolysed by a current of 3 A passing for 1 hour. What is the charge of palladium ions in solution if 2.977g of Pd ions are reduced at cathode?       [+4]

Q21. Calculate the e.m.f. of the cell: Cr(s)|Cr³⁺(0.1M)||Fe²⁺(0.01M)|Fe(s).   Given: E^o Cr³⁺|Cr  = - 0.75V,       E^o Fe²⁺|Fe  = - 0.45 V.

Q22. Calculate standard electrode potential of Ni²⁺/Ni if the cell potential of the cell:  Ni(s)|Ni²⁺(0.01M)||Cu²⁺(0.1M)|Cu(s) is 0.59V. Given: Cu²⁺/Cu = 0.34V.              [- 0.2205 V]

Q23. For the cell, Mg(s)|Mg²⁺(aq)||Ag⁺(aq)|Ag(s), calculate the equilibrium constant at 25⁰C and also the maximum work that can be obtained by operating the cell.                                  E^o ( Mg²⁺|Mg)  =  - 2.37V, E^o (Ag⁺|Ag) = + 0.80 V.