Based on chemical reactions, into how many types of titration is titrimetric analysis divided?

Direct titration, Back titration, Displacement titration, Indirect titration

Direct titration method: The so-called direct titration method is a technique in which a standard solution is used to directly titrate the substance being analyzed. Any chemical reaction that meets all three of the above conditions can be analyzed using the direct titration method. Direct titration is the most common and fundamental titration method in titrimetric analysis. For example, titrating NaOH with HCl, or titrating Fe2+ with K2Cr2O7, etc. Often, some chemical reactions cannot meet all three requirements of titrimetric analysis; in such cases, one of the following methods can be used for titration. Back-titration method: The direct titration method cannot be used in the following situations. First, when the reaction between the substance to be measured in the test solution and the titrant is slow, such as the reaction between Al3+ and EDTA, or when the substance to be measured has hydrolytic properties. Second, when directly titrating a solid sample with a titrant, the reaction does not complete immediately. Such as the titration of solid CaCO3 with HCl. Third, in cases where there is no suitable indicator for certain reactions, or when the substance being analyzed inhibits the action of the indicator, such as in the titration of Cl– with AgNO3 in acidic solutions, there is no appropriate indicator available. For these aforementioned problems, the back-titration method is usually employed. Back-titration involves first adding a precise amount of excess standard solution so that it reacts with the substance of interest or the solid sample present in the test solution; after the reaction is complete, another standard solution is used to titrate the remaining standard solution. For example, in the titration of Al3+ mentioned above, a known excess of EDTA standard solution is added first; once the reaction between Al3+ and EDTA is complete, the remaining EDTA is back-titrated using standard Zn2+, Pb2+, or Cu2+ solutions ； For the titration of solid CaCO3, an excess of HCl standard solution is added first; once the reaction is complete, the remaining HCl can be back-titrated using standard NaOH solution ； For the titration of Cl– in acidic solutions, an excess of AgNO3 standard solution can be added first to completely precipitate the Cl–; thereafter, a trivalent iron salt is used as an indicator, and NH4SCN standard solution is used to back-titrate the excess Ag+. The endpoint is reached when a pale red color appears. Displacement titration: For certain substances that cannot be directly titrated, it is possible to first react them with another substance to displace a certain amount of a substance that can be titrated, and then titrate that substance using an appropriate titrant. This titration method is called displacement titration. For example, sodium thiosulfate cannot be used to directly titrate potassium dichromate and other strong oxidizing agents, because in acidic solutions these oxidizing agents can oxidize S2O32– to mixtures such as S4O62– or SO42–, with no fixed stoichiometric relationship. However, sodium thiosulfate is an excellent titrant for titrating iodine. In this way, if an excess of potassium iodide is added to an acidic potassium dichromate solution, a certain amount of iodine is displaced by potassium dichromate, and then the iodine is directly titrated with a standard sodium thiosulfate solution; the stoichiometric relationship becomes very good. In practical work, this method is used to standardize the concentration of the sodium thiosulfate standard solution using potassium dichromate. Indirect titration method: Some substances, although they cannot undergo a chemical reaction directly with the titrant, can be determined indirectly through other chemical reactions. For example, the determination of calcium using the potassium permanganate method belongs to the indirect titration method. Since Ca2+ has no variable valence states in solution, it cannot be directly titrated by redox methods. However, if Ca2+ is first precipitated as CaC2O4, filtered and washed, then dissolved with H2SO4, and the C2O42– bound to Ca2+ is titrated using a KMnO4 standard solution, the calcium content can be determined indirectly. Clearly, the application of back-titration, displacement titration, and indirect titration **has expanded the scope of application of titrimetric analysis.

They can be basically classified into the following types: 1. Acid-base titration (including non-aqueous acid-base titration), used to determine acidic or basic substances; an indicator or potentiometry can be used to indicate the end point. 2. Redox titration (including Karl Fischer titration for water determination), used to determine substances with redox properties; an indicator or potentiometry can be used to indicate the end point. 3. Precipitation titration, used to determine substances that can form precipitates; an indicator or potentiometry can be used to indicate the end point. 4. Complexometric titration, used for transition metals and alkaline earth metals; generally, an indicator is used to indicate the end point. 5. Phase transition titration, commonly used in the study or analysis of phase compositions; it is rarely used in routine analysis, with the end point usually determined visually

It can be divided into acid-base titration, complexometric titration, redox titration, and precipitation titration, etc.

This post was last edited by ask123456 on 2009-11-17 10:05. Based on chemical reactions, titrimetric analysis is divided into four types: (the four major titration methods). Acid-base titration: A titrimetric analysis method that relies on proton transfer reactions between acids and bases in water. It can be used to determine acids, bases, and amphoteric substances. Its basic reaction is H++OH-=H2O; it is also known as the neutralization method, and it is a volumetric analysis technique that makes use of acid-base reactions. Complexometric titration: A volumetric analysis method based on complexation reactions. Also known as chelation titration. It primarily uses amine carboxylate chelating agents as titrants, which have a strong chelating capacity for many metals. Commonly used aminocarboxylate chelating agents include nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), cyclohexanediaminetetraacetic acid (DCTA), triethylenetetraminepentaacetic acid (DTPA), and ethylene glycol diethyl ether diaminetetraacetic acid (EGTA); more than 95% of chelation titrations are carried out using these agents. Redox titration: Redox titration is a titrimetric analysis method based on the transfer of electrons between oxidants and reductants in a solution. Compared to acid-base titration and complexometric titration, redox titration is widely used; it can be applied not only in inorganic analysis but also in organic analysis, as many organic compounds with oxidizing or reducing properties can be determined using redox titration. Precipitation titration: It is a titrimetric analysis method based on precipitation reactions. Conditions that must be met for precipitation titration: 1. S should be small, and the titration should be able to be completed quantitatively ； 2. Fast reaction speed ； 3. An appropriate indicator is used to indicate the endpoint ； 4. The adsorption phenomenon does not affect the observation of the endpoint. 　　There are many reactions that produce precipitates, but few of them meet the requirements for volumetric analysis. In practice, the silver method is the most commonly used; it relies on the reaction between Ag+ and halide ions to determine Cl-, Br-, I-, SCN-, and Ag+.

Be more precise with the questions: Reaction type: direct, indirect, substitution, retrograde, …; Reaction mechanism: redox, acid-base, … Please check the relevant information again; I don’t remember it very clearly

:Lol, the four major titrations in chemistry are something that those who study chemistry must know.

This is the analysis area; in my opinion, there are some types of questions related to RZ that shouldn’t be asked. First, there’s the bad intention of earning points (mainly by participating in discussions). Second, it undermines the quality expected of managers. Third, it suggests a lack of respect for those who contribute to the analysis section

A forum is a place where everyone actively exchanges ideas, discusses, and learns. In my opinion, everyone has their own role and strengths, so problems vary in difficulty; what matters is participation. Everyone is encouraged to participate in order to earn participation points; this is the rule of the forum, and I don’t see anything unreasonable about it. Managers should actively manage the forum posts and promptly address those that violate the forum rules. For normal discussion posts, an attitude that supports diversity should be adopted. Furthermore, paying attention to details and accumulating knowledge bit by bit from small issues is a necessary process for everyone to learn and grow. Personally, I think knowledge is for one’s own use, and it has no necessary connection with what others think.