Question

The formula of exhausted permutit is _____
[A] $CaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$
[B] $NaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$
[C] $Ca{{B}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$
[D] ${{K}_{2}}A{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$

Answer 1

Hint: Permutit is also the common name for man made zeolite. Zeolite is a hydrated sodium aluminosilicate compound. We obtain exhausted permutit in the process of water softening where the water hardness causing ions replaces the cations in the zeolite.

Complete step by step answer:
Permutit is the common name of zeolite. Artificial zeolites are called permutit.
We know that zeolite is a hydrated sodium aluminosilicate. It is a natural mineral and there are around fifty zeolites. Zeolites have different types and sources.
Zeolites are capable of exchanging its sodium ions. They can exchange their sodium ions reversibly for hardness creating ions in water. Generally hardness if water is caused due to presence of oxides of calcium and magnesium.
Zeolites can release their sodium cation and form a complex with ions like calcium and magnesium.
We use this property of zeolites for softening of water.
General formula of zeolites is $NaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$. This is also known as the permutit.
The exhausted permutit is the compound left behind after the zeolite has undergone ion exchange with it. In the process of water softening, the sodium ion is often replaced by calcium ions. Thus the exhausted permutit has calcium in it.
The formula of exhausted permutit becomes $CaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$.
So, the correct answer is “Option A”.

Note: Zeolite is also used as a shape selective catalyst due to its uniform shape and size of the micropores. In a catalytic reaction, where zeolite is used, the molecules of the reactant are diffused in the pores of the mineral i.e. The molecule is trapped inside it and is later adsorbed in the active sites of the chemical reaction.