Question

How is a back titration in the lab carried out?

Answer 1

The titration which is performed in reverse is called back titration. In the process of back titration, excess of standard known reagent is mixed in the solution and then the excess is titrated. Back titration has performed in different conditions as given below.

Complete step by step answer:
-In the process of back titration, the concentration of an analyte is determined. Determination takes place by treating the analyte with a known amount of excess standard reagent. After that the remaining excess standard reagent is then titrated with another reagent. The second result of titration will determine the quantity of excess reagent used in the titration firstly performed. After that the concentration of the original analyte can be calculated. Back titration is also known as an indirect titration.
-A back titration is performed in such a condition when the molar concentration of an excess reactant is known, but we have to determine the concentration of an analyte.
-Mostly back titration is applied in acid-base titrations with some conditions as given below:
-When the acid or base is an insoluble salt (for example calcium carbonate)
-When the end point in normal titration is hard to determine (for example weak acid and weak base titration)
-And when the reaction occurs very slowly
-More commonly, back titration is performed when it is hard to determine the end point in normal titration. It applies to some precipitation reactions.

Note:
There are two steps which are typically followed in a back titration first of them is that the volatile analyte reacts with an excess reagent and secondly A titration is conducted on the remaining quantity of the known solution. This is a way to measure the amount consumed by the analyte, thus calculate the excess quantity.