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Questions and Answers
What is the main purpose of adding ammonium chloride solution in the procedure?
What is the main purpose of adding ammonium chloride solution in the procedure?
The color change from wine red to pure blue indicates the end point of the titration.
The color change from wine red to pure blue indicates the end point of the titration.
True
What is the molarity of the disodium EDTA solution used in the procedure?
What is the molarity of the disodium EDTA solution used in the procedure?
0.05 M
In gravimetric analysis, the purity of the precipitate is essential for accurate ___ measurements.
In gravimetric analysis, the purity of the precipitate is essential for accurate ___ measurements.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Which of the following is NOT a common step in gravimetric analysis?
Which of the following is NOT a common step in gravimetric analysis?
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In acid-base titration, the titrant is typically a strong acid or base.
In acid-base titration, the titrant is typically a strong acid or base.
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What role does Mordan black IT play in the titration process?
What role does Mordan black IT play in the titration process?
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What is the primary focus of gravimetry?
What is the primary focus of gravimetry?
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Gravimetry relies on the conversion of ions or elements to pure form through precipitation reactions.
Gravimetry relies on the conversion of ions or elements to pure form through precipitation reactions.
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Name one of the steps involved in gravimetry.
Name one of the steps involved in gravimetry.
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Gravimetry often involves the __________ reaction to measure the amount of a substance.
Gravimetry often involves the __________ reaction to measure the amount of a substance.
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Which of the following is NOT a characteristic of precipitation titrations?
Which of the following is NOT a characteristic of precipitation titrations?
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Polarography is utilized for measuring the concentration of elements in solution using electricity.
Polarography is utilized for measuring the concentration of elements in solution using electricity.
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In acid-base titrations, the point at which the reaction is complete is called the __________ point.
In acid-base titrations, the point at which the reaction is complete is called the __________ point.
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Match the following analysis methods with their characteristics:
Match the following analysis methods with their characteristics:
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What should not be present when using titration in basic solutions?
What should not be present when using titration in basic solutions?
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Volhard's method was designed for determining the presence of important drugs.
Volhard's method was designed for determining the presence of important drugs.
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Who designed Volhard's method?
Who designed Volhard's method?
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Silver __________ is produced during the titration process in a basic solution.
Silver __________ is produced during the titration process in a basic solution.
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Match the compounds with their relevant applications:
Match the compounds with their relevant applications:
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Which of the following ions can cause problems during titration?
Which of the following ions can cause problems during titration?
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Titration can be effectively used in the presence of many anions.
Titration can be effectively used in the presence of many anions.
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What important method is used in the determination of silver hydroxide?
What important method is used in the determination of silver hydroxide?
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Study Notes
Precipitation Titration
- Precipitation titrations involve chemical reactions that form a colored, insoluble precipitate.
- Standard solutions and reaction substances react to form the precipitate.
Types of Precipitation Titration
- Mohr's method
- Volhard's method
- Modified Volhard's method
- Fajans' method
Mohr's Method
- An important precipitation titration method developed by Karl Friedrich Mohr in 1856.
- Potassium chromate (K₂CrO₄) is used as an indicator.
- Silver nitrate (AgNO₃) is titrated against a 2% potassium chromate solution in a neutral environment.
- The formation of brick-red silver chromate (Ag₂CrO₄) indicates the end point.
Volhard's Method
- A back titration method designed by Jacob Volhard in 1874.
- Involves the titration of excess silver nitrate (AgNO₃).
- A standard thiocyanate solution is used.
- The endpoint is marked by the appearance of a reddish-brown color as a ferric thiocyanate complex.
Fajans' Method
- Introduced by Fajans in 1923-24.
- Uses adsorption indicators.
- The indicator adsorbs on the precipitate, changing color at the endpoint.
- Adsorption indicators change color at the equivalence point, signaling the end of the reaction. (Fluorescein, eosin, and others)
- Silver chloride (AgCl) precipitate is formed
Limitations of Mohr's method
- Not suitable for basic solutions.
- Ammonia ions and other multivalent anions interfere.
Pharmaceutical applications of Mohr's method
- Determination of chloride ions in sodium chloride and dextrose injections.
- Determination of bromide, thiocyanate ions.
- Determination of other anions.
Complexometric Titration
- A titration method in which the formation of a coloured complex indicates the endpoint.
- It is used to determine the concentration of various metal ions present in a solution.
- Ethylenediaminetetraacetic acid (EDTA) is frequently used
- It is also known as chelometric titration or chelatometric titration.
Principles of Complexometric Titration
- Metal ions are titrated against chelating agents or complexing agents.
- It involves changing simple metal ions into complex ions via indicator use, to determine the endpoint.
- EDTA is often used as a complexing agent.
- The reaction results in a color change, helping determine the endpoint.
Types of Complexometric Titrations
- Direct titrations,
- Back/Indirect titrations,
- Replacement titrations, and
- Alkalimetric titrations.
Gravimetric Analysis
- Quantitative analysis involves finding the precise weight or amount of a substance in its pure form (precipitate).
- Involves performing precipitation reactions to transform materials into solid form for determination and measurement.
Steps Involved in Gravimetric Analysis
- Sampling
- Precipitation
- Dissolution/Ostwald Ripening
- Filtration
- Washing
- Drying/Ignition
- Weighing
- Calculation
Types of Impurities in Precipitates
- Co-precipitation (impurities absorbed onto the surface or trapped inside the precipitate during growth),
- Post-precipitation (impurities adsorbed onto the precipitate's surface or exterior after precipitate is formed).
Estimation of Barium Sulphate
- Gravimetrically determining the amount of barium sulfate (BaSO₄).
- Dilute sulphuric acid (H₂SO₄) is added to a barium chloride (BaCl₂) solution to precipitate barium sulphate (BaSO₄).
- The precipitate is then filtered, washed, dried, and weighed.
Redox Titration
- A type of redox reaction where a known amount of oxidant or reductant is used to determine the unknown amount of reductant or oxidant, respectively, in the sample.
- Oxidation : loss of electrons.
- Reduction : gain of electrons.
Iodimetry
- A form of redox titration that uses iodine (I₂) as the titrant.
- Determination of reducing agents typically with standard sodium thiosulfate (Na₂S₂O₃).
Iodometry
- A redox titration method that uses iodide ions as the reactant.
- This technique uses the reaction of the analyte with iodide to free iodine.
- Standard sodium thiosulfate is then used to titrate the liberated iodine
Polarography
- An electrochemical method. Involves measuring the current flow between an electrode and a solution, commonly a dropping mercury electrode.
- Helps in the determination of the analyte concentration and its properties during redox reactions and current flow.
- Used to determine the concentration of metal ions in solutions. Uses an indicator electrode and a reference electrode to study the behavior of analyte and its reduction potential. Uses an indicator.
Potentiometry
- Measures differences in Electrical potential between reference and indicator electrodes.
- Used to analyze the analyte concentration in solutions.
- Electrochemical method that measures voltage between electrodes.
- Uses the Nernst equation to calculate the analyte's concentration based on voltage measurements.
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Description
Explore various methods of precipitation titration, including Mohr's, Volhard's, and Fajans' methods. This quiz covers the principles behind each method and their specific indicators. Test your understanding of the chemical reactions involved in forming precipitates.
