Precipitation Titration and Complex Titration PDF

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M8 Activity 4 Activity for Lessons 4 & 5 Research on Precipitation Titrations and Complexation Titrations. Details are as follows: Answer the following details for each type of Titration. A. Objective & Importance B. Substances Involved in the Process of Titration and their characteristics C. Conditions Required in the Titration D. Limitations in using the method of Titration E. Types if any & differentiate each F. Sample Problem

Precipitation Titrations A. Objective & Importance Precipitation titration is a type of titration in which the formation of precipitate occurs as a result of the titration procedure itself. It is a method in which the titrant reacts with the analyte to form an insoluble substance known as a precipitate and it will proceed until the last drop of analyte has been utilized. This procedure is carried out in as follows: • Determining the number of halide ions present in a solution. • Assessing the amount of salt present in food items. • Used for Sulphur, thiocyanate, dichromate. • Through precipitate titration you can evaluate different drugs such as carbromal, KCl infusion, NaCl infusion etc. • Determine the concentration of anions in the analyte. B. Substances Involved in the Process of Titration and their characteristics • Titrant – The "known" solution is the titrant, which has a precise and accurate concentration. In most cases, it is a strong acid or base. • Analyte – The analyte is the "unknown" solution whose concentration or equilibrium constant you desire to determine. It can be either acidic or basic, and it can be weak or strong. Due to the fact that titration is a neutralization procedure, acid analytes are titrated with strong bases and basic analytes with strong acids.

Examples of indicators • • • C.

Chromate ion (Mohr's method) Fluorescein (Fajans method) Iron ion (volhard method)

Conditions Required in the Titration • It should be a very rapid reaction. • It should be a single suitable stoichiometry reaction. • It should show the change in the concentration of the reactants or products at the end point.

D. . Limitations in using the method of Titration • Precipitation Titration is only used for quantitative determinations not for qualitative evaluations. • Interferences are more such as coprecipitation, occlusion, etc. E. Types if any & differentiate each • Volhard’s method Titration of bromides, iodides, and chlorides in an acidic medium is required for this method. When excess silver nitrate solution is added to the solution, the chloride is converted to silver chloride. The remaining silver nitrate is weighed against a solution of potassium thiocyanate. When the thiocyanate completely consumes the silver, the remaining thiocyanate is made to react with an indicator. When combined with ferric ammonium sulfate indicator, it produces a red color, and a ferrous thiocyanate complex is formed. •

Modified Volhard’s method When analyzing chloride, the volhard method must be slightly modified. During the titration, the solution is brought into contact with two precipitation stimulants simultaneously: silver chloride and ammonium thiocyanate, which have varying solubilities.

•

Fajan’s method The Fajan's method is a precipitation titration in which silver ion is titrated with halide or thiocyanate ions in the presence of an adsorption indicator. The indicator is a dye that exists in solution as an ionized form of typically anion.

•

Mohr method This method measures chlorides in neutral solutions. In acidic conditions, chromate ion protonates chromic acid. So, it doesn't precipitate. Silver hydroxide is formed in highly alkaline solutions. This brown formation denotes the endpoint.

F. Sample Problem Titrate a solution with silver nitrate to determine its chloride ion concentration (whose concentration is known). During titration, a white precipitate of AgCl can be seen at the flask's bottom and the amount of silver ion used equals the amount of chloride ion originally present. • •

To calculate the number of moles of chloride ion or silver ion we can use: n = cV To calculate the volume of the added solution or molar concentration of ion the corresponding values of either of the ions should be known.

Mohr Titrations:

Volhard Titration:

Complexation Titration A. Objective & Importance Complexometric titration is a type of volumetric analysis in which the formation of a colored complex serves as a marker for the titration's end point. It is particularly useful for determining the concentration of a solution containing a mixture of different metal ions. Because EDTA is capable of forming stable 1:1 complex ion with a wide variety of metal ions, it can be used to determine the concentrations of these metal ions in a solution via titrations. The reactions used in these titrations involve the formation of complex ions, they are called complexometric titration. It is used in analytical chemistry to perform the assay. It is used to determine: • Concentration of metal ions in sample solutions • Amount of calcium present in food products • Cosmetic Products • Total hardness of the water • Concentration metal is in a pharmaceutical dosage form in a drug • Bad metals B. Substances Involved in the Process of Titration and their characteristics. It is based on complex formation between metal ion (cation) and complexing agent (ligand). • Metal ion indicator In a solution, a metal ion indicator is a substance that changes color when it binds to metal ions. Metal ion indicators are typically polyprotic complexing agents, which means they can bind to multiple metal ions at the same time. (eg EDTA, Ethylenediaminetetraacetic acid) • Ligand A complex is the end product of a complexation reaction. The species that donates electron pairs by acting as a Lewis base is referred to as a complexing agent or ligand, while the Lewis acid that accepts the donated electrons is referred to as the central ion or central atom. C. Conditions Required in the Titration When performing metal cation titrations with EDTA, a complexometric indicator is almost always required to determine when the end point has been reached. Organic dyes such as Fast Sulphon Black and Eriochrome Black T are frequently used as indicators. When the endpoint is reached, the indicator is displaced (typically by EDTA) from the metal cations in solution. Thus,

rather than the metal complex, the free indicator serves as the endpoint indicator. D. Limitations in using the method of Titration •

• •

It is a dangerous technique that frequently necessitates the use of relatively large amounts of the substance under examination as well as large chemical waste. Due to the open nature of this method, certain variables such as humidity, pH, and temperature can influence the results. This necessitates the occurrence of reactions in the liquid phase, which is generally undesirable due to the chemical being studied.

E. Types if any & differentiate each Types of Titrations with EDTA •

Direct titration: The cations are titrated directly with standard solution EDTA, with the indicator eriochrome black T serving as an indicator.

•

Back Titration: Analytical back titration involves adding a known excess of standard solution EDTA to the analyte solution. A final step involves titration with a magnesium or zinc standard solution containing eriochrome black T. This method can be used to determine the concentration of cations that form stable complexes with EDTA but lack an effective indicator. It is also used to treat ions that react slowly with EDTA.

•

Indirect Titration: EDTA can be used as an anion titrant. Precipitation of anions is possible using a suitable metal ion. Filter and wash the presentation with the appropriate solution. Then, add excess EDTA to the boiling solution to complex the metal ion.

•

Displacement Titration: An excess of a second metal bound to EDTA is added to the analyte. The analyte ion depletes the EDTA complex of the second metal, which is then titrated with EDTA.

F. Sample Problem •

Direct titration:

•

Back Titration:

REFERENCES: Precipitation Titration - Definition, Types & Example. (n.d.). VEDANTU; www.vedantu.com. Retrieved April 17, 2022, from https://www.vedantu.com/chemistry/precipitation-titration

Precipitation Titration - Definition, Example, Types, Indicators of Precipitation Titration. (2020, February 5). BYJUS; byjus.com. https://byjus.com/chemistry/precipitation-titration/ Titrations. (n.d.). ch302.cm.utexas.edu. Retrieved April 18, 2022, from http://ch302.cm.utexas.edu/chemEQ/neutralizations/selector.php?name=titration s#:~:text=The%20analyte%20is%20the%20%22unknown,be%20either%20weak %20or%20strong. Precipitation Titrations. (2016, December 2). Precipitation Titrations; rxpharmaworld.blogspot.com. http://rxpharmaworld.blogspot.com/2016/12/precipitationtitrations.html#:~:text=Conditions%20Required%20for%20the%20Precipitation,p roducts%20at%20the%20end%20point. What is difference between volhard and modified volhard method? – Raiseupwa.com. (n.d.). What Is Difference between Volhard and Modified Volhard Method? – Raiseupwa.Com; www.raiseupwa.com. Retrieved April 18, 2022, from https://www.raiseupwa.com/popular-guidelines/what-is-differencebetween-volhard-and-modified-volhard-method/ 304.4: Complex ion Equilibria and Complexometric Titrations - Chemistry LibreTexts. (2019, January 26). Chemistry LibreTexts; chem.libretexts.org. https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Mo dules_(Analytical_Chemistry)/Quantifying_Nature/Volumetric_Chemical_Analysi s_(Shiundu)/14.4%3A_Complex_ion_Equilibria_and_Complexometric_Titrations Complexometric Titrations. Retrieved from: http://www.csun.edu/~hcchm003/321/321120313.pdf. (n.d.). KIRUTHIGA, B. (n.d.). https://webstor.srmist.edu.in/web_assets/srm_mainsite/files/downloads/Complex ometric_Titration.pdf. Complexometric Titration. Principle and types of complexometric titration. (2021, July 15). Chrominfo: Principle and Types of Complexometric Titration; chrominfo.blogspot.com. https://chrominfo.blogspot.com/2021/07/principle-and-types-of-complexometrictitration.html#Types%20of%20complexometric%20titration...