Fajan's Method and Dyes Quiz

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Questions and Answers

Which titration uses the appearance of a precipitate as the endpoint detection method?

Titration of CN- by Ag+

Titration of Cl- and Br- by AgNO3 (correct)

Titration of Ag+ by SCN-

Titration of Ag+ by CN-

In Mohr's method, the medium must be neutral or slightly alkaline to prevent the conversion of chromate into what?

Dichromate (correct)

Chromic acid

Chromium trioxide

Chromic oxide

In Fajan's method of endpoint detection in precipitimetry, what is used?

Soluble colored complexes

Adsorption indicators (correct)

Redox indicators

Colored precipitates

In Fajan's method, when are acidic dyes preferentially adsorbed by the precipitate at the equivalence point?

Titration of AgNO3 with chloride or bromide ion Signup and view all the answers

In Fajan's method, when are basic dyes preferentially adsorbed by the precipitate at the equivalence point?

Titration of CN- with Ag+ Signup and view all the answers

What type of indicator is used in Fajan's method of endpoint detection in precipitimetry?

Adsorption indicators Signup and view all the answers

In Fajan's method, which type of dye is preferentially adsorbed by the precipitate when titrating AgNO3 with chloride or bromide ions?

Acidic dyes Signup and view all the answers

What is the purpose of the adsorption indicators used in Fajan's method?

To change color when adsorbed by the precipitate at the equivalence point Signup and view all the answers

Which of the following is a requirement for the successful use of adsorption indicators in Fajan's method?

The indicator dye ion must be opposite in charge with the precipitating titrant ion Signup and view all the answers

In Mohr's method, what is the required medium for the titration?

Neutral or slightly alkaline medium Signup and view all the answers

Which method is used to titrate Ag+ by CN-?

Lang's method Signup and view all the answers

Which method is used to determine Cl- and Br- by AgNO3 using chromate ion as an indicator?

Mohr's method Signup and view all the answers

Under which pH conditions are weak acidic dyes, such as fluorescein, used in Fajan's method?

Slightly acidic Signup and view all the answers

Which dye can be used at pH 4 in Fajan's method?

Fluorescein Signup and view all the answers

Why can't eosin be used for Cl determination in Fajan's method?

It has no opposite charge to the precipitating titrant ion Signup and view all the answers

True or False: One of the requirements for the successful use of adsorption indicators in Fajan's method is that the indicator dye ion must have the opposite charge to the precipitating titrant ion.

True Signup and view all the answers

True or False: Basic dyes are used in Fajan's method in an acidic medium to ensure their ionization.

False Signup and view all the answers

True or False: Eosin can be used for Cl- determination in Fajan's method.

False Signup and view all the answers

Study Notes

Precipitimetry

Mohr's Method uses the appearance of a precipitate as the endpoint detection method.
In Mohr's method, the medium must be neutral or slightly alkaline to prevent the conversion of chromate into dichromate.
Fajan's Method uses adsorption indicators for endpoint detection in precipitimetry.
Acidic dyes are preferentially adsorbed by the precipitate at the equivalence point in Fajan's method when the precipitate has a positive charge.
Basic dyes are preferentially adsorbed by the precipitate at the equivalence point in Fajan's method when the precipitate has a negative charge.
In Fajan's method, the type of indicator used is an adsorption indicator.
When titrating AgNO3 with chloride or bromide ions in Fajan's method, anionic dyes are preferentially adsorbed by the precipitate.
The purpose of adsorption indicators in Fajan's method is to change color when adsorbed onto the precipitate at the equivalence point.
Successful use of adsorption indicators in Fajan's method requires that the precipitate forms a well-defined, compact layer at the equivalence point, which is essential for adsorption.
Mohr's method requires a neutral or slightly alkaline medium for the titration.
Liebig's method is used to titrate Ag+ by CN-.
Mohr's method is used to determine Cl- and Br- by AgNO3 using chromate ion as an indicator.
In Fajan's method, weak acidic dyes are used in a slightly acidic medium (pH 3-4) to ensure their ionization and adsorption onto the precipitate.
Fluorescein (pH 4) can be used in Fajan's method.
Eosin cannot be used for Cl determination in Fajan's method because chlorides do not bind to it strongly enough.
True: One of the requirements for the successful use of adsorption indicators in Fajan's method is that the indicator dye ion must have the opposite charge to the precipitating titrant ion.
False: Basic dyes are used in Fajan's method in an alkaline medium to ensure their ionization.
False: Eosin cannot be used for Cl- determination in Fajan's method because chlorides do not bind to it strongly enough.

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Description

Test your knowledge on Fajan's method and dyes used in different pH conditions. Questions cover the use of weak acidic dyes like fluorescein, pH conditions for specific dyes, and limitations of certain dyes in the method.