10/18/2025
UNIT-III
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
The Mohr's method is a precipitation titration used to determine the concentration of chloride or bromide
ions in a solution. It is a direct titration method that uses silver nitrate as the titrant and potassium chromate
as an indicator.
Principle of Mohr's Method: The principle is based on the formation of colored precipitates at the endpoint.
1.Silver ions ( +) from the silver nitrate solution react with the chloride ions ( −) in the sample to form a
white precipitate of silver chloride ( ). This reaction continues until all the chloride ions are precipitated.
+( )+ −( )→ ( )( ℎ )
2.Potassium chromate ( 2 4) is used as an indicator.The Mohr's method is a precipitation titration used to
determine the concentration of chloride ( −) ions in a solution. It involves a direct titration with a standard
silver nitrate ( 3) solution using potassium chromate ( 2 4) as an indicator.
, 10/18/2025
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
+( )+ −( )→ ( )( ℎ ) Primary Reaction
2 +( )+ 2−4( )→ 2 4( )( ℎ− ) Endpoint Detection
Procedure: The general procedure for the Mohr's method is as follows:
1.Preparation: Pipette a known volume of the chloride sample (NaCl/NS) solution into a
conical flask. Dilute it with distilled water if necessary.
2.Add Indicator: Add a small amount (e.g., 1 mL) of potassium chromate indicator solution to
the flask. The solution will turn a faint yellow color.
3.Titration: Titrate the solution with a standardized silver nitrate solution from a burette,
swirling the flask continuously.
4.Endpoint: Continue titrating until the color of the solution changes permanently from yellow
to a faint reddish-brown. This color change indicates the endpoint. The volume of silver nitrate
used is recorded.
5.Calculation: The concentration of chloride ions in the original sample can be calculated using
the stoichiometry of the reaction and the volume of silver nitrate consumed
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
Based on the principle of the Mohr's method, the calculation formula is derived from the stoichiometric
relationship between the moles of silver nitrate and the moles of chloride ions at the endpoint.
The primary reaction is: ++ −→ ( )
The molar ratio of silver ions to chloride ions is 1:1. Therefore, at the endpoint:
3= −
The number of moles can be calculated using the formula: = ( )× ( )
So, the calculation formula becomes: 3× 3= −× −
Where:
3= Concentration of the standard silver nitrate solution (in Molarity, M)
3= Volume of silver nitrate solution used in the titration (in Liters, L)
− Concentration of the chloride solution (in Molarity, M)
=
−= Volume of the chloride sample solution taken for titration (in Liters, L)
You can rearrange this formula to solve for the unknown chloride concentration:
, 10/18/2025
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
i. Suggest type of analytical method can be used.
ii. Discuss brief procedure for the same.
iii. Derive reaction and factor.
iv. Why acidic pH is not suitable for titration
v. Write Pharmaceutical application of suggested method.
Appropriate analytical method for quantifying the amount of halide in a liquid
formulation at pH 7 is argentometric titration. This is a type of precipitation titration
that uses a silver nitrate ( 3) solution as the titrant. The specific type of
argentometric titration that is suitable for a neutral pH is the Mohr's method.
The analyst working in the laboratory wants to quantify the amount of Precipitation Titration
halide present in a liquid formulation having pH 7.
ii. Discuss brief procedure for the same: Procedure for Mohr's method to quantify
chloride ions is as follows:
Preparation: Take a known volume of the halide-containing liquid formulation and place it
in a conical flask.
Indicator addition: Add a small amount of potassium chromate ( 2 4) solution, which
acts as the indicator, to the flask.
Titration: Titrate the solution with a standardized solution of silver nitrate ( 3) from a
burette.
Endpoint detection: The silver ions ( +) from the titrant will first react with the halide ions
( −) to form a silver halide precipitate (e.g., silver chloride, ). Once all the halide ions
have been precipitated, the first excess drop of silver nitrate will react with the chromate
indicator to form a reddish-brown precipitate of silver chromate ( 2 4). This color
change signals the endpoint of the titration.
, 10/18/2025
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
iii. Derive reaction and factor.
The primary reactions for the Mohr method are:
Precipitation of halide: The silver ions react with the halide ions to form a silver halide
precipitate.
+( )+ −( )→ ( )↓
Endpoint reaction: After all the halide has reacted, the excess silver ions react with the
chromate indicator to produce a brick-red precipitate.
2 +( )+ 2−4( )→ 2 4( )↓
The factor, also known as the equivalent weight, relates the mass of the analyte (halide)
to the mass of the titrant (silver nitrate). In this 1:1 reaction, one mole of 3 is
equivalent to one mole of the halide ( −). The gravimetric factor for a specific halide
would be its molar mass divided by the molar mass of 3
For example, the factor for chloride ( −) would be the molar mass of −divided by the
molar mass of 3
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
iv. Why acidic pH is not suitable for titration
The Mohr's method requires a neutral or slightly alkaline pH, typically between 7 and
10. An acidic pH is not suitable because it affects the chromate indicator. In an acidic
solution, the chromate ion ( 2−4) converts to dichromate ( 2 2−7) or chromic acid
( 2 4), which significantly lowers the concentration of chromate ions. This
conversion prevents the formation of the reddish-brown silver chromate precipitate at
the endpoint, leading to an inaccurate result.
At higher pH silver ions may be removed by precipitation with hydroxide ions, and
at low pH chromate ions may be removed by an acid-base reaction to form hydrogen
chromate ions or dichromate ions, affecting the accuracy of the end point.
UNIT-III
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
The Mohr's method is a precipitation titration used to determine the concentration of chloride or bromide
ions in a solution. It is a direct titration method that uses silver nitrate as the titrant and potassium chromate
as an indicator.
Principle of Mohr's Method: The principle is based on the formation of colored precipitates at the endpoint.
1.Silver ions ( +) from the silver nitrate solution react with the chloride ions ( −) in the sample to form a
white precipitate of silver chloride ( ). This reaction continues until all the chloride ions are precipitated.
+( )+ −( )→ ( )( ℎ )
2.Potassium chromate ( 2 4) is used as an indicator.The Mohr's method is a precipitation titration used to
determine the concentration of chloride ( −) ions in a solution. It involves a direct titration with a standard
silver nitrate ( 3) solution using potassium chromate ( 2 4) as an indicator.
, 10/18/2025
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
+( )+ −( )→ ( )( ℎ ) Primary Reaction
2 +( )+ 2−4( )→ 2 4( )( ℎ− ) Endpoint Detection
Procedure: The general procedure for the Mohr's method is as follows:
1.Preparation: Pipette a known volume of the chloride sample (NaCl/NS) solution into a
conical flask. Dilute it with distilled water if necessary.
2.Add Indicator: Add a small amount (e.g., 1 mL) of potassium chromate indicator solution to
the flask. The solution will turn a faint yellow color.
3.Titration: Titrate the solution with a standardized silver nitrate solution from a burette,
swirling the flask continuously.
4.Endpoint: Continue titrating until the color of the solution changes permanently from yellow
to a faint reddish-brown. This color change indicates the endpoint. The volume of silver nitrate
used is recorded.
5.Calculation: The concentration of chloride ions in the original sample can be calculated using
the stoichiometry of the reaction and the volume of silver nitrate consumed
Precipitation Titration
Elaborate the principle and procedure for the titration of Chloride
using Silver nitrate by Mohr’s method.
Based on the principle of the Mohr's method, the calculation formula is derived from the stoichiometric
relationship between the moles of silver nitrate and the moles of chloride ions at the endpoint.
The primary reaction is: ++ −→ ( )
The molar ratio of silver ions to chloride ions is 1:1. Therefore, at the endpoint:
3= −
The number of moles can be calculated using the formula: = ( )× ( )
So, the calculation formula becomes: 3× 3= −× −
Where:
3= Concentration of the standard silver nitrate solution (in Molarity, M)
3= Volume of silver nitrate solution used in the titration (in Liters, L)
− Concentration of the chloride solution (in Molarity, M)
=
−= Volume of the chloride sample solution taken for titration (in Liters, L)
You can rearrange this formula to solve for the unknown chloride concentration:
, 10/18/2025
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
i. Suggest type of analytical method can be used.
ii. Discuss brief procedure for the same.
iii. Derive reaction and factor.
iv. Why acidic pH is not suitable for titration
v. Write Pharmaceutical application of suggested method.
Appropriate analytical method for quantifying the amount of halide in a liquid
formulation at pH 7 is argentometric titration. This is a type of precipitation titration
that uses a silver nitrate ( 3) solution as the titrant. The specific type of
argentometric titration that is suitable for a neutral pH is the Mohr's method.
The analyst working in the laboratory wants to quantify the amount of Precipitation Titration
halide present in a liquid formulation having pH 7.
ii. Discuss brief procedure for the same: Procedure for Mohr's method to quantify
chloride ions is as follows:
Preparation: Take a known volume of the halide-containing liquid formulation and place it
in a conical flask.
Indicator addition: Add a small amount of potassium chromate ( 2 4) solution, which
acts as the indicator, to the flask.
Titration: Titrate the solution with a standardized solution of silver nitrate ( 3) from a
burette.
Endpoint detection: The silver ions ( +) from the titrant will first react with the halide ions
( −) to form a silver halide precipitate (e.g., silver chloride, ). Once all the halide ions
have been precipitated, the first excess drop of silver nitrate will react with the chromate
indicator to form a reddish-brown precipitate of silver chromate ( 2 4). This color
change signals the endpoint of the titration.
, 10/18/2025
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
iii. Derive reaction and factor.
The primary reactions for the Mohr method are:
Precipitation of halide: The silver ions react with the halide ions to form a silver halide
precipitate.
+( )+ −( )→ ( )↓
Endpoint reaction: After all the halide has reacted, the excess silver ions react with the
chromate indicator to produce a brick-red precipitate.
2 +( )+ 2−4( )→ 2 4( )↓
The factor, also known as the equivalent weight, relates the mass of the analyte (halide)
to the mass of the titrant (silver nitrate). In this 1:1 reaction, one mole of 3 is
equivalent to one mole of the halide ( −). The gravimetric factor for a specific halide
would be its molar mass divided by the molar mass of 3
For example, the factor for chloride ( −) would be the molar mass of −divided by the
molar mass of 3
Precipitation Titration
The analyst working in the laboratory wants to quantify the amount of
halide present in a liquid formulation having pH 7.
iv. Why acidic pH is not suitable for titration
The Mohr's method requires a neutral or slightly alkaline pH, typically between 7 and
10. An acidic pH is not suitable because it affects the chromate indicator. In an acidic
solution, the chromate ion ( 2−4) converts to dichromate ( 2 2−7) or chromic acid
( 2 4), which significantly lowers the concentration of chromate ions. This
conversion prevents the formation of the reddish-brown silver chromate precipitate at
the endpoint, leading to an inaccurate result.
At higher pH silver ions may be removed by precipitation with hydroxide ions, and
at low pH chromate ions may be removed by an acid-base reaction to form hydrogen
chromate ions or dichromate ions, affecting the accuracy of the end point.
