TYPES OF REDOX TITRATIONS and Differences: MCQ for GPAT, NET JRF, GATE exam

Types of Redox titrations :-

  1. IODIMETRY
  2. IODOMETRY
  3. CEREMETRY
  4. PERMANGNOMETRY
  5. POTASSIUM DICHROMATE TITRATIONS
  6. POTASSIUM IODATE TITRATIONS

TITRATIONS INVOVLING IODINE :-

One of the most common redox titration involve either using iodine (I2)as a mild oxidizing agent or iodide (I¯) as a mild reducing agent.

1. IODIMETRY :-  

  • covers the titrations with a standarded solutions of iodine.
  • Direct method
  • Titrant is I2 and analyte is reducing agent.

2. IODOMETRY :-

  • Deals with the titration of iodine liberated in chemical reaction.
  • The iodine librated is titrated with standared solution of sodium thiosulphate.
  • Indirect method
  • Free I2 is convereted to I¯ ion with reducing agent.
  • Most accuracy method for determing the percentage of oxidizing and reducing agent.
  • Standardisation of secondary standard sodium thiosulphate can be done with potassium dichromate and potassium iodate.
  • commercial iodine is often contaminated hence is purified by sublimation.It is very slightly soluble in water.(0.335g/litre).
  Direct iodimetric method Indirect iodometry
Titrating agent Iodine for determination of reducing agents I is added to oxidizing agents the librated I2 is titr. With Na2S2O3.
Indicator Added at the beginning of tit. Added near the end of titr.
Type of reaction One step Two steps
Standard solution Iodine Sodium thisoufate
E.P. Permanent blue Disappearance of blue colour

OTHER TITRATIONS ARE :-

  1. CEREMETRY
  2. PERMANGNOMETRY
  3. POTASSIUM DICHROMATE TITRATIONS
  4. POTASSIUM IODATE TITRATIONS

INDICATORS USED IN REDOX TITRATIONS (REDOX INDICATORS)

Redox Indicators are themselves an oxidant or reductant. Oxidised, form has one colour and reduced form has other colour. When shlight excess of oxidant is present. the Indicator changes its colour and Is shown as end point of the titration. There are different methods of dete
point of redox titrntions. They
1. Self indicators
2. External Indicators
3. Redox indicators
4. Instrumental techniques
1. Self Indicators
The oxidised or reduced form of the titrant or the substance itself self indicating. eg. Cerric Ions are yellow coloured and are reduced to colourless Ions before the end point is shown by the yellow colour due to excess of cerric ions.

2.EXTERNAL INDICATOR

In iodine titration- blue color complex formed.  Solution remain colorless upto equivalence point- fraction of drop turn solution blue

3.Redox indicator
weak reducing or oxidizing agent,
“End point depend on-potential at given point Nernst equation-use to calculate potential

4.Instrumental technique 

By using potentiometer or conductometer we are determined end point.

APPLICATION OF REDOX TITRATIONS USING CAS

  1. Acetomenapthone tablets
  2. Ascorbic acid tablets
  3. Chlorpromazine tablets
  4. Ferrous fumarate tablets
  5. Ferrous gluconate tablets
  6. Iron dextron injection
  7. Iron sorbitol injection
  8. Paracetamol

MCQ 

1.Which sentence is flase about iodimetry ?

a.Covers the titrations with a standarded solutions of iodine.

b.Direct method

c.Titrant is I2 and analyte is reducing agent.

d.Free I2 is convereted to I¯ ion with reducing agent

2. Which sentence is flase about iodometry ?

a.Titrant is I2 and analyte is reducing agent.

b.The iodine librated is titrated with standared solution of sodium thiosulphate.

c.Deals with the titration of iodine liberated in chemical reaction.

d.Most accuracy method for determing the percentage of oxidizing and reducing agent.

3.Which indicator are example of self indicator ?

a. sudan red

b. Methylen blue

c. Cerric Ions

d. Orange fe

4.Which  instrument is used to detection of end point ?

a. Potentiometer

b. Conductometer

c. a and b

d. None of the above

5. Which drug is not assay by redox titration ?

a.Acetomenapthone tablets

b.Ascorbic acid tablets

c.Chlorpromazine tablets

d.Metformin

6. Which drug is assay by redox titration ?

a. Metformin

b.Cinchonism

c.Digioxin

d.Ferrous gluconate tablets

ANSWER KEY 

1.C

2.A

3.C

4.C

5.D

6.D

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REFERENCE :-

PHARMACEUTICAL ANALYSIS THIRD EDITION OF DR. RAVI SANKAR (PGNO. 20.1-20.7).

 

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