Question

Which of the following cannot give iodometric titrations?
(A) \[F{e^{3 + }}\]
(B) \[C{u^{2 + }}\]
(C) \[P{b^{2 + }}\]
(D) \[A{g^ + }\]

Answer 1

Hint: When titrated with standardised thio-sulphate solution then the solution's colour changes in an iodometric titration from a deep blue to pale yellow. This signifies the titration's conclusion. The resulting response is \[{\text{I}}_3^ - + {\text{2}}{{\text{S}}_2}{\text{O}}_3^{2 - } \to {{\text{S}}_4}{\text{O}}_6^{2 - } + 3{{\text{I}}^ - }\].

Complete Step by Step Solution:
As we know that the iodometric titration is the end point of an iodometric titration, sometimes referred to as iodometry, is determined by the emergence or disappearance of elementary iodine. Iodine released during the process is indirectly measured during this titration.

Let's now discuss the given options to determine the correct response:
In the first option, we have \[F{e^{3 + }}\]. As we know that\[F{e^{3 + }}\]is an iron \[(III)\] refers to the element iron in its \[ + 3\] oxidation state. In an ionic compound like salts, such an atom may occur as a separate cation with a positive ion that is denoted by \[Fe\] .
Ferrous iron oxidises to form ferric iron, which is rust. And this type of iron is filterable and one backwashing iron filter, the Terminox Iron, Sulphur and Manganese filter can get rid of both.

Now, let’s notice the second option \[C{u^{2 + }}\], The homogeneous transition metal compound class of inorganic compounds includes copper \[(2 + )\], also known as \[Cu\,(II)\] or copper \[(II)\] ion. These are inorganic compounds having just metal atoms, with a transition metal atom serving as the biggest atom.

Consider the third option \[P{b^{2 + }}\], we know that the lead Acetate is another name for lead \[(II)\]. A white, crystalline chemical substance with the formula \[Pb{({C_2}{H_3}{O_2})_2}\] is called acetate. It is dangerous to consume lead acetate. It serves as a mordant in dyeing and is used to create white lead for use in medications.

The last option \[A{g^ + }\], a chemical element silver \[(A{g^ + })\], a white, shiny metal prized for both its aesthetic appeal and electrical conductivity. Between copper \[(Period\,4)\] and gold \[(Period\,6)\], silver is in\[Group\,11(Ib)\] and \[(Period\,5)\] of the periodic table. As a result, both its physical and chemical characteristics are midway between those of those two metals.
Therefore, the correct answer is the indicator used in iodometric titrations is lead acetate \[(P{b^{2 + }})\].
Thus, the correct option is: (C) \[P{b^{2 + }}\].

Note: It should be noted that due to the difficulty of dissolving molecular iodine \[({I_2})\] in water, potassium iodide is added to the titration. Iodometric and iodometric titrations can occasionally be mistaken with one another.