Question

The estimation of available chlorine in bleaching powder is done by
(a) Acid-base titration
(b) Permanganometric titration
(c) Iodimetric titration
(d) Iodometric titration

Answer 1

For these questions, we have to know that given titrations are used for estimation for which elements and which one will be better for the estimation of the available chlorine in bleaching powder.

Complete step-by-step answer: We start with the uses of all the given titration methods:
Acid-base titration: This type of titration is used for the determination of the unknown concentrations of the acids or base present in the solution, by neutralizing with an acid or base of the known concentration. (Neutralization: The process in which acid and base reacts with each other to form salt and water.)
Permanganometric titration: In this titration, permanganates are used to measure the quantity of the analyte present in the samples. It is also known as the redox reaction because in these methods, the concentration of the analyte is determined by causing a redox reaction with the titrant and the analyte.
Iodimetric titration: This type of titration is useful for determining the properties of substances having reducing properties. This is also called Iodimetry. It is used for reducing agents.
Iodometric titration: This type of titration is generally used for determination of concentration of an oxidising agent in the solution. It is also known as Iodometry. The appearance and disappearance of iodine, indicates the end point. It is used for determining the oxygen samples or active chlorines in the water bodies.
As the active chlorine is present in the bleaching powder, so, from the above discussion, Iodometric titration is used for the estimation of available chlorine in bleaching powder.

Hence, the correct option is (d) Iodometric titration.

Note: There is a minor difference between the iodometric concentration and iodimetric concentration, in iodometric titration is indirectly titrated with the iodine whereas in the iodimetric titration is directly titrated with the iodine.