Types of Precipitation Titration: Volhard's Method

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What type of reactions are dealt with in volumetric precipitimetry?

Reactions that require the formation of relatively insoluble substances or precipitates

Which principle can be applied to all precipitation reactions in volumetric analysis?

Solubility product principle

What historical method was used for the quantitative analysis of inorganic pharmaceutical products containing metal ions?

Gravimetric methods

What analytical reagent revolutionized metal determination in volumetric analysis?

Disodium ethylenediaminetetraacetate (EDTA) Signup and view all the answers

What are the three learning outcomes for students at the end of the unit in Pharmaceutical Analysis I?

<ol> <li>Understand and explain the principles in the analysis of pharmaceuticals using volumetric analysis method. 2. Differentiate the application of each type/method of volumetric analysis. 3. Perform assay and solve the percentage purity of samples.</li> </ol> Signup and view all the answers

How is metal determination performed using EDTA in volumetric analysis?

By employing metal-ion indicators in the same manner that pH indicators are used in acid-base titrations Signup and view all the answers

What is the principle of precipitation titration?

The quantity of reagent added is equal to the precipitate obtained. Signup and view all the answers

What are the requirements for precipitation titration?

<ol> <li>The precipitate formation must be stoichiometric. 2. The equilibrium between precipitate and its ions must be attained rapidly. 3. The precipitate must have low solubility indicated by a small equilibrium constant (Ksp). 4. A method to detect the stoichiometric point must be available.</li> </ol> Signup and view all the answers

Explain the chemical reaction involved in the precipitation titration of chloride ion with silver nitrate.

AgNO3 (aq) + KCl (aq) -> AgCl (s) + KNO3 Signup and view all the answers

What is the best method for detecting the endpoint in precipitation titration?

Argentometric Titration Signup and view all the answers

Why is it important for the precipitate to have low solubility in the solution in precipitation titration?

To ensure that the equilibrium is reached rapidly and the titrant can be added quickly. Signup and view all the answers

What type of reaction is required in precipitation titration to ensure sufficient completion?

Formation of insoluble substances (precipitates) or appearance of turbidity. Signup and view all the answers

What is the purpose of Volhard's method in precipitation titration?

To determine halide (F, Cl, Br, I) ions and anions (phosphate, chromate) in acidic medium. Signup and view all the answers

Who introduced Fajan's method in precipitation titration?

Kazimierz Fajan, an American chemist. Signup and view all the answers

What indicator is used in Volhard's method?

Ferric alum. Signup and view all the answers

How is the end point determined in Fajan's method?

The end point is determined when the indicator adsorbs onto the surface of the silver salt precipitate and causes a color change. Signup and view all the answers

What is the titrant used in the assay of Phenylmercuric nitrate?

0.1 N NH4SCN. Signup and view all the answers

Which method uses potassium chromate as an indicator?

Fajan's method. Signup and view all the answers

What is the indicator used in Mohr's Method for titrating chloride ions?

Potassium chromate Signup and view all the answers

What conditions should be maintained for Volhard's Method to titrate halides?

Acidic conditions Signup and view all the answers

Why is it important for the conditions to be neutral to alkaline in Mohr's Method?

To prevent the formation of iron hydroxide ions Signup and view all the answers

Which metal ions can be titrated using Disodium ethylenediaminetetracetic acid (EDTA) as a complexing agent?

Aluminum, Bismuth, Calcium, Magnesium, and Zinc Signup and view all the answers

What is the role of a ligand in complexation reactions?

Provide groups for attachment to metal ions Signup and view all the answers

Why is titration of iodide and cyanate not possible in Mohr's Method?

Due to the formation of a reddish brown precipitate with silver chromate Signup and view all the answers

What is the purpose of a masking agent in the context of chelate determination?

To render the metals in the sample inactive. Signup and view all the answers

How can masking be achieved during the determination of metal ions?

By adjusting the pH of the titration medium or using auxiliary complexing agents (masking agents). Signup and view all the answers

Give an example of a substance used as a masking agent in the presence of aluminum and magnesium EDTA complexes.

Triethanolamine. Signup and view all the answers

Which substance is used to mask Hg and Cu to enable the titration of Zn at pH 6?

Thioglycols. Signup and view all the answers

Name a substance that masks Co, Ni, Cu, and Zn during chelate determination.

Potassium cyanide. Signup and view all the answers

Which method involves the determination of Ca, Mg, and Zn compounds using EDTA as the titrant?

Direct titration method. Signup and view all the answers