11. Estimation of Iron content (Fe2+) by Potentiometric Titration

VIVA – VOICE QUESTIONS & ANSWERS

11. Estimation of Iron content (Fe²⁺) by Potentiometric Titration

1. What is emf.

Electromotive force is defined as, "the difference of potential which causes flow of current from one electrode of higher potential to the other electrode of lower potential.

2. What is the standard solution used in this titration.

K₂Cr₂O₇

3. What is the name of the instrument used here.

Potentiometer

4. What is the basic principle of potentiometric titration.

Emf of a cell depends on the concentration of the electrolytes with which the electrodes are in contact. Therefore, the electrode reaction is,

As the concentration of Mⁿ⁺ changes, the emf of the cell also changes correspondingly.

5. Why does emf increase during the titration.

When it is titrated against the standard K₂Cr₂O₇ solution, taken in the burette, the emf is going on increasing as the concentration of Fe³⁺ increases due to the following reaction.

6. What is the name of the indicator electrode used in this titration.

Platinum electrode

7. What is the name of the reference electrode used here, write it representation.

Calomel electrode; Hg/Hg₂Cl₂, KCl

8. Write the cell representation of the titration.o

The cell is set up by connecting this redox electrode with a calomel electrode as shown below

Hg / Hg₂Cl_2(s), KC1// Fe²⁺, Fe³⁺ / Pt

9. What is redox reaction.

Redox reaction is a chemical reactions, where oxidation occurs in one half and reduction occurs in another part.

10. Write the nernst equation of a cell.

11. What are the advantages of potentiometric titrations.

(i) The necessary apparatus required is cheap and easily available.

(ii) This method can be used for coloured solution.

(iii) Fixing up end point is easier when compared to the titrations in which indicators are used to fix up end points.

(iv) Very dilute solutions can be titrated with accuracy.

(v) Several components may be titrated in the same solution.

12. How will you obtain the end point in the titration.

The accurate end point is determined by plotting ΔE/ΔV Vs Volume of K₂Cr₂O₇ added.

13. What is the equivalent weight of Fe²⁺ ion.

55.85

14. How will you calculate the amount of Fe²⁺ ions.

Amount of Fe²⁺ = 55.85 × N gms/lit