How acetylsalicylic acid is determined by acid base titration?

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How acetylsalicylic acid is determined by acid base titration?

Aspirin is a weak acid that also undergoes slow hydrolysis; i.e., each aspirin molecule reacts with two hydroxide ions. To overcome this problem, a known excess amount of base is added to the sample solution and an HCl titration is carried out to determine the amount of unreacted base.

What is titration method for assay of aspirin?

Dissolve ASA sample in 5 ml ethanol 95 % and then add 25 ml of 0.5 N NaOH, the container of the mixture was stoppered and allowed to stand for ½ hour to complete the hydrolysis of ASA. 1-2 drops of bromophenol blue (bpb) indicator was added and the solution was titrated with 0.5 N HCl. The endpoint is pink  colorless.

What is a back titration?

A technique in volumetric analysis in which a known excess amount of a reagent is added to the solution to be estimated. The unreacted amount of the added reagent is then determined by titration, allowing the amount of substance in the original test solution to be calculated.

Why do we titrate aspirin with NaOH?

Part II: Determination of the purity of aspirin tablets Second, you will titrate a sample of your aspirin (acetylsalicylic acid) with the standardized NaOH to determine the moles of acid in a given weight of your product. This will allow you to assess its purity.

What is a back titration with antacid?

The excess HCl is titrated with NaOH(aq) until enough OH– (from the NaOH solution) has been added to completely react with the excess H+ (from the excess HCl in the solution). So, part of the added acid is neutralized by the antacid tablet; the remainder is neutralized by the NaOH added. This is called back titration.

What is the purpose of a back titration?

A back titration is used when the molar concentration of an excess reactant is known, but the need exists to determine the strength or concentration of an analyte. Back titration is typically applied in acid-base titrations: When the acid or (more commonly) base is an insoluble salt (e.g., calcium carbonate)

What is back titration PPT?

BACK TITRATIONBack titration is a process in which theexcessof a standard solution used toconsume an analyte is determined bytitration with a second standard solution. Example: Lab 3b ( Determination ofacetylsalicylic acid in aspirin) )1.

Why do we do back titrations?

What is the aim of back titration experiment?

What is back titration example?

BACK TITRATION Back titration is a process in which the excess of a standard solution used to consume an analyte is determined by titration with a second standard solution. Example: Determination of acetylsalicylic acid in aspirin. Sometime direct titration of an analyte with a reagent is not FEASIBLE.

What is back titration method?

Updated on October 07, 2019. A back titration is a titration method where the concentration of an analyte is determined by reacting it with a known amount of excess reagent. The remaining excess reagent is then titrated with another, second reagent.

What is the purpose of back titration?

Back titration or indirect titration is commonly used when the reaction is very slow, the endpoint of the normal titration method is difficult to determine and it is also used for some precipitation titrations.

What is back titration?

Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated.

What is the principle involved in back titration?

How is a back-titration performed? A back titration is performed according to the following general principle: Add reagent B in excess to analyte A. Allow reagent B to react with analyte A. This might require a certain waiting time or even refluxing (e.g., saponification value).

Why is it called a back titration?

Back titration is also titration. It is called back titration because it is not carried out with the solution whose concentration is required to be known (analyte) as in the case of normal or forward titration, but with the excess volume of reactant which has been left over after completing reaction with the analyte.

What is back titration also known as?

A back titration may also be called an indirect titration.

Why can’t I titrate aspirin for titration?

Many reactions are slow or present unfavorable equilibria for direct titration. Aspirin is a weak acid that also undergoes slow hydrolysis; i., each aspirin molecule reacts with two hydroxide ions. To overcome this to determine the amount of unreacted base.

Is aspirin an acid or base?

How do you determine the concentration of aspirin?

Determination of Aspirin using Back Titration This experiment is designed to illustrate techniques used in a typical indirector backtitration. You will use the NaOH you standardized last week to back titrate an aspirin solution and determine the concentration of aspirin in a typical analgesic tablet.

Can You titrate aspirin with NaOH?

You will use the NaOH you standardized last week to back titrate an aspirin solution and determine the concentration of aspirin in a typical analgesic tablet. You will be graded on your accuracy. Required Reading D.C. Harris, Quantitative Chemical Analysis (7th ed., W. H. Freeman, NY, 2007) p. 121-122. PreLab Quiz Topics