Question

Which one of the following is used for reviving the exhausted permutit?

• A. $ \text{HCl} $ solution
• B. $ \text{10 }\!\!%\!\!\text{ }\,\,\text{CaC}{{\text{l}}_{\text{2}}} $ solution
• C. $ \text{10 }\!\!%\!\!\text{ }\,\text{MgC}{{\text{l}}_{\text{2}}} $ solution
• D. $ \text{10 }\!\!%\!\!\text{ NaCl} $ solution

Answer 1

Answer: (B)

During the softening process the reaction takes place as: $ N{{a}_{2}}Ze+CA{{(HC{{O}_{3}})}_{2}}\xrightarrow{{}}CaZe $ $ +2NaHC{{O}_{3}} $ $ N{{a}_{2}}Ze+Mg{{(HC{{O}_{3}})}_{2}}\xrightarrow{{}}MgZe $ $ +2NaHC{{O}_{3}} $ After sometime, the zeolite is completely converted into calcium and magnesium zeolites. Eventually, the bed ceases to soften water i.e., it gets exhausted. At this stage the supply of hard water is stopped and the exhausted zeolite is reclaimed by treating the bed with a 10% NaCI solution (Brine soln.) when the following reaction takes place: $ CaZe\,or\,MgZe+2NaCl\xrightarrow{{}} $ $ \underset{\text{Reclaimed}\,\text{zeolite}}{\mathop{N{{a}_{2}}Ze}}\,+CaC{{l}_{2}}\,or\,MgC{{l}_{2}} $