Question

In a permutit, the calcium and magnesium ions of hard water are exchanged by:
A) $C{{O}_{3}}^{2-}$ and $HC{{O}_{3}}^{-}$ ions of permutit.
B) $N{{a}^{+}}$ ions of permutit
C) $A{{l}^{3+}}$ ions of permutit
D) $S{{i}^{4+}}$ ions of permutit

Answer 1

Hint: The answer here is based on the technique used for softening hard water and ions responsible for hardening of water are exchanged by zeolite that is nothing but permutit. Thus, the correct answer can be guessed on this fact.

Complete Solution :
In the chapters of chemistry, we have come across the several concepts of inorganic chemistry that deals with the concepts about the purification process and also about the methods involved to obtain the pure components from a metal ore.

- Now we shall see what permutit means and how is the process carried out.
- Permutit is basically a trade name given for synthetic zeolite. Zeolite has the composition of${{M}_{{}^{2}/{}_{n}}}OA{{l}_{2}}{{O}_{3}}.xSI{{O}_{2}}.y{{H}_{2}}O$

- Here, M is the charge balancing non framework cation having valency ’n’, ‘x’ is the value from 2.0 or more and ‘y’ is the number of moles of water in the voids.

- Permutit is sodium aluminium ortho silicate having formula $N{{a}_{2}}A{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O$
- Permutit occurs in the form of sand where $C{{a}^{2+}}$ or $M{{g}^{2+}}$ ions are filtered through sand and is exchanged by sodium ions.

- Since, calcium and magnesium ions are responsible for the hardness of water, permutit process indulges in its purification and the equation is as shown below,
\[N{{a}_{2}}A{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O+C{{a}^{2+}}(M{{g}^{2+}})\to Ca(Mg)A{{l}_{2}}S{{i}_{2}}{{O}_{8}}.x{{H}_{2}}O+2N{{a}^{+}}\]
So, the correct answer is “Option B”.

Note: You must be thorough with the trade name as well as the common name given for the ores and note that these names are given which has slight changes from the actual composition of that particular synthetic compound.