
The indicator used in iodometric titrations is
A. Phenolphthalein
B. Litmus
C. Potassium iodide
D. Starch
Answer
510.9k+ views
Hint: In an iodometric titration, the solution changes its colour from deep blue to light yellow when titrated with standardized thiosulfate solution. This marks the end point of the titration. The reaction involved is .
Complete answer:
Let us first understand what is iodometric titration; Iodometric titration is also known as Iodometry is a method of volumetric analysis and a redox titration where the appearance or disappearance of elementary iodine indicates the end point. This titration involves indirect titration of iodine liberated by the reaction.
Let us now discuss the options to know the correct answer-
A. Phenolphthalein: Phenolphthalein is a chemical compound with the formula , which is represented as . It is used as an indicator in acid–base titrations. The completion of reaction is indicated by colour change as it turns colourless in acidic solutions and pink in basic solutions.
B. Litmus: A commonly used and natural indicator is litmus. It is extracted from lichens. It turns purple in neutral solutions. Litmus indicator turns red in acidic solutions and blue in alkaline solutions.
C. Potassium Iodide: Aqueous potassium iodide (KI) has a light orange-brown colour. It is used for testing the presence of oxidising agents; It is also used in iodometric solutions.
D. Starch: In iodometric titration, sodium thiosulphate, (a reducing agent) is used specifically to titrate iodine. It is a general method to determine the concentration of an oxidising agent in solution. In an iodometric titration, a starch solution is used as an indicator as it can absorb the that is released.
The correct answer is the indicator used in iodometric titrations is starch
So, the correct answer is “Option D”.
Additional Information:
Applications of iodometry:
(1)- When an excess amount of standard iodine solution is added to the known volume of sample. Sulphites reduce iodine readily in acidic medium to iodide, the sulphites present reduces iodine quantitatively:
(2)- Iodometry is useful in volumetric analysis. Like, the determination of copper (II) and chlorate. The reactions include and .
(3)- This method is used to analyze the concentration of oxidising agents in water samples such as active chlorine in swimming pools.
Note:
Potassium iodide is added to the titration as molecular iodine ( ) is not easily soluble in water. Sometimes, we get confused between iodometric and iodimetric titrations,
Complete answer:
Let us first understand what is iodometric titration; Iodometric titration is also known as Iodometry is a method of volumetric analysis and a redox titration where the appearance or disappearance of elementary iodine indicates the end point. This titration involves indirect titration of iodine liberated by the reaction.
Let us now discuss the options to know the correct answer-
A. Phenolphthalein: Phenolphthalein is a chemical compound with the formula
B. Litmus: A commonly used and natural indicator is litmus. It is extracted from lichens. It turns purple in neutral solutions. Litmus indicator turns red in acidic solutions and blue in alkaline solutions.
C. Potassium Iodide: Aqueous potassium iodide (KI) has a light orange-brown colour. It is used for testing the presence of oxidising agents; It is also used in iodometric solutions.
D. Starch: In iodometric titration, sodium thiosulphate,
The correct answer is the indicator used in iodometric titrations is starch
So, the correct answer is “Option D”.
Additional Information:
Applications of iodometry:
(1)- When an excess amount of standard iodine solution is added to the known volume of sample. Sulphites reduce iodine readily in acidic medium to iodide, the sulphites present reduces iodine quantitatively:
(2)- Iodometry is useful in volumetric analysis. Like, the determination of copper (II) and chlorate. The reactions include
(3)- This method is used to analyze the concentration of oxidising agents in water samples such as active chlorine in swimming pools.
Note:
Potassium iodide is added to the titration as molecular iodine (
IODOMETRY | IODIMETRY |
Quantitative analysis of an oxidising agent by iodide that on reaction forms iodine, which is then titrated. | Volumetric analysis which involves the titration with a standardized solution of iodine. |
Iodide reacts with another oxidising agent in an acidic medium. | Uses free iodine that reacts with reducing agent in an acidic medium. |
It is a direct method. | It is an indirect method. |
It quantifies oxidising agents. | It quantifies reducing agents. |
Latest Vedantu courses for you
Grade 11 Science PCM | CBSE | SCHOOL | English
CBSE (2025-26)
School Full course for CBSE students
₹41,848 per year
Recently Updated Pages
Master Class 12 Business Studies: Engaging Questions & Answers for Success

The reciprocal of 0 is class 7 maths CBSE

The least number by which 216 must be divided to make class 7 maths CBSE

On selling 17 balls at Rs 720 there is a loss that-class-7-maths-CBSE

Which religion believes in strict monotheism A Hinduism class 7 social science CBSE

Express 13overline2+0overline35 as a fraction in the class 7 maths CBSE

Trending doubts
Father of Indian ecology is a Prof R Misra b GS Puri class 12 biology CBSE

Who is considered as the Father of Ecology in India class 12 biology CBSE

Enzymes with heme as prosthetic group are a Catalase class 12 biology CBSE

A deep narrow valley with steep sides formed as a result class 12 biology CBSE

An example of ex situ conservation is a Sacred grove class 12 biology CBSE

Why is insulin not administered orally to a diabetic class 12 biology CBSE
