Question

Which of the following can act as a good mordant?
(A) $SnC{l_4}$
(B) $SnC{l_2}$
(C) $PbC{l_2}$
(D) $Pb{I_4}$

Answer 1

Hint: Mordant is the chemical used to fix the dye on the substance and form an insoluble compound.

Complete Step by Step Solution:
A chemical dye is a colored substance used to add colour to the other substance by applying it over it. Mordant is the substance used to fix the chemical dye over the substrate. There are different mordants like the salt of Copper (Cu), Iron (Fe), Aluminium (Al), Tin (Sn), Sodium (Na), and Potassium (K).

Mordants are mostly polyvalent metals. So it easily reacts with dye or stains and forms a colloidal coordination complex. A covalent bond is formed between hydroxyl and oxygen in the mordant and dye. Also, a coordinate bond is formed with other oxygen atoms. This coordination complex helps the dye bond with the fabric. This complex has a higher molecular weight than the dye. So it is difficult to wash away the dye.

Among the given mordants, $SnC{l_4}$ acts as a good mordant.
Because it easily gets hydrolyzed with water and forms hydroxides.
$SnC{l_4} + 4{H_2}O \to Sn{(OH)_4} + 4HCl$
This Stannic hydroxide easily forms the colloidal coordination complex and makes a dye bond with the fabric.
SnCl₂ forms insoluble salt during hydrolysis. So, it cannot be a good mordant.
PbCl₂ does not dissolve in water. So, it cannot be a good mordant.
PbI₄ does not exist.
Compared to other mordants, SnCl₄ acts as a good mordant.

Note: Mordants are a substance that helps the dye material to attach to fabric for a long time. A substance that is easily hydrolyzed acts as good mordants.