Download PTU M-Sc -Chemistry 2nd Semester May 2019 51152 ELECTROCHEMICAL TECHNIQUES Question Paper

Roll No.

Total No. of Pages : 02

Total No. of Questions: 19

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M.Sc.(Chemistry) (Campus) (2015 to 2017) (Sem.-2)

ELECTROCHEMICAL TECHNIQUES

Subject Code : CHL-415

M.code: 51152

Time: 3 Hrs.

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Max. Marks : 70

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains SIX questions carrying FIVE marks each and students have to attempt ALL questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

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SECTION-A

1. What is the role of liquid junction potential?
2. Given that E(Zn²⁺/Zn) = -0.76V and E(Cu²⁺/Cu) = +0.34V . Identify the cathode and anode of the electrochemical cell.
3. Write down the relation between specific conductance and equivalent conductance.
4. Why calomel electrode is called reversible electrode?

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5. What is anodic depolarizer? Give one example.
6. Write Nernst equation with meaning of the parameters involved.
7. How do you test for the irreversibility of a redox reaction in CV?
8. Mention the limitation of direct current polarography.
9. Draw the conductometric titration curve of weak acid with strong base.

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10. How concentration cells are different from electrochemical cells?

SECTION-B

11. For the following cells, write down the cell reactions and calculate the EMF at 298K.
    (a) Ag(s)|Ag⁺(a = 0.1) || Zn²⁺(a° = 0.1)|Zn
    Given the following standard potential values :
    

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    E(Ag⁺/Ag) = 0.799V; E(Zn²⁺/Zn) = -0.763V; Predict whether the cell reaction is spontaneous or not.
12. Write a short note on linear sweep voltammetry (LSV).
13. What is log-plot in polarography? Mention its characteristic physical significance.
14. The molar conductances of CH₃COONa, HCl and NaCl at infinite dilution are 91×10^-4, 426×10^-4 and 126×10^-4 Sm²mol^-1 respectively at 25°C. Calculate the molar conductance at infinite dilution for CH₃COOH.
15. Mention the merits and demerits of dropping mercury electrode (DME) used in polarography.

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16. Write a short note on oscillometry.

SECTION-C

17. Construct the Frost diagram of manganese from the following scheme :
    MnO₄ --> MnO₂ ?MN³⁺ ? Mn²⁺ ? Mn
    From this diagram justify that :
    

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    a) Mn³⁺ is unstable,
    b) MnO₂ is an oxidising agent,
    c) Mn²⁺ is the usual product of reduction of Mn (VII).
    Can you use a nickel spatula to stir a solution of copper sulphate? Explain.
18. Differentiate between cathodic and anodic stripping methods. Draw a typical excitation signal and voltammogram in case of striping method. Define microelectrode and mention its advantages.

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19. Specific conductance of a decimolar solution of KC1 at 18°C is 1.12 Sm^-1.The resistance of a conductivity cell containing the solution at 18°C was found to 55 O. Calculate the cell constant.
    What is the effect of dilution on :
    a) The specific conductance
    b) The equivalent conductance of CH₃COOH.

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