Table of Contents
Why do we use back titration instead of direct 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. When direct titration endpoint would be hard to discern (e.g., weak acid and weak base titration) When the reaction occurs very slowly.
Why is back titration performed?
A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions. Back titrations are also useful if the reaction between the analyte and the titrant is very slow, or when the analyte is in a non-soluble solid.
What is back and blank titration?
Back titration is also referred to as indirect titration. Blank Titration. A blank titration is carried out by titrating a fixed and known concentration of titrant into a solvent with zero analyte. The only difference from the regular titration is the absence of analyte.
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.
What is back titration of aspirin?
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 happens during saponification of esters?
During saponification, ester reacts with an inorganic base to produce alcohol and soap. Generally, it occurs when triglycerides are reacted with potassium or sodium hydroxide (lye) to produce glycerol and fatty acid salt, called ‘soap’.
What is a back titration and why is it used?
A back titration is necessary in situations where the reaction you are using to analyse the unknown substance is too slow to respond in a normal titration. In titration, you need the reaction to be able to reach a definite endpoint at practically the same moment as you have reached the stoichiometric equivalence point.
What is saponification in chemistry?
In terms of chemistry saponification can be define as the reaction of ester with water and base such as NaOH or KOH to give alcohol and sodium or potassium salt of the acid. The oils which go through the saponification reaction are known as saponified oils. Saponified oils are mixed with sodium hydroxide and water.
What is the saponification value of potassium oxide?
Saponification value is a measure of the content of ester linkages. It is determined by back titration of potassium oxide in the presence of phenolphthalein indicator with 0.5 N sulfuric or hydrochloric acid.39 First a sample is mixed with 25 ml of alcoholic solution of KOH and left for 1 h in steam bath to react.