Question:
Match the water softening methods in List-1 with the chemicals/reagents in List-2:
[h]
{|l|l|}
List -1 (Method) & List -2 (Reagent)
(A) Calgon method & (I) RSO\(_3\)H
(B) Ion exchange method & (II) Ca(OH)\(_2\)
(C) Clark's method & (III) NaAlSiO\(_4\)
(D) Synthetic resin method & (IV) Na\(_6\)(PO\(_3\))\(_6\)
Match the water softening methods in List-1 with the chemicals/reagents in List-2:
[h]
{|l|l|}
List -1 (Method) & List -2 (Reagent)
(A) Calgon method & (I) RSO\(_3\)H
(B) Ion exchange method & (II) Ca(OH)\(_2\)
(C) Clark's method & (III) NaAlSiO\(_4\)
(D) Synthetic resin method & (IV) Na\(_6\)(PO\(_3\))\(_6\)
(A) Calgon method & (I) RSO\(_3\)H
(B) Ion exchange method & (II) Ca(OH)\(_2\)
(C) Clark's method & (III) NaAlSiO\(_4\)
(D) Synthetic resin method & (IV) Na\(_6\)(PO\(_3\))\(_6\)
Show Hint
Remember:Calgon =Complex (Sodium hexametaphosphate),Clark's =Calcium hydroxide (Lime). This "C" mnemonic helps distinguish the two chemical methods.
Updated On: Jun 3, 2026
- A-III, B-IV, C-II, D-I
- A-IV, B-III, C-II, D-I
- A-IV, B-I, C-II, D-III
- A-III, B-I, C-IV, D-II
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Concept:
Water softening is the process of removing calcium, magnesium, and certain other metal cations in hard water. Various chemical and physical methods are used:
• Calgon method: Uses sodium hexametaphosphate to form complex soluble salts with calcium and magnesium ions.
• Ion exchange method (Permutit): Uses zeolites (hydrated sodium aluminum silicate) to exchange sodium ions with hardness-causing ions.
• Clark's method: A chemical method involving the addition of a calculated amount of lime to remove temporary hardness.
• Synthetic resin method: Uses organic polymers with acidic or basic groups (like sulfonic acid groups) for cation/anion exchange.
Step 1: Matching Calgon method.
Calgon is a trade name forSodium hexametaphosphate, represented by the formulaNa\(_6\)(PO\(_3\))\(_6\). Therefore,A matches with IV.
Step 2: Matching Ion exchange and Clark's method.
The Ion exchange method (Zeolite process) usesSodium aluminum silicate, formulaNaAlSiO\(_4\). Therefore,B matches with III. Clark's method specifically involves the addition ofSlaked lime, formulaCa(OH)\(_2\), to precipitate carbonates. Therefore,C matches with II.
Step 3: Matching Synthetic resin method.
Synthetic resins used for cation exchange are large organic molecules containing groups like-SO\(_3\)H (sulfonic acid groups), represented asRSO\(_3\)H. Therefore,D matches with I.
• Calgon method: Uses sodium hexametaphosphate to form complex soluble salts with calcium and magnesium ions.
• Ion exchange method (Permutit): Uses zeolites (hydrated sodium aluminum silicate) to exchange sodium ions with hardness-causing ions.
• Clark's method: A chemical method involving the addition of a calculated amount of lime to remove temporary hardness.
• Synthetic resin method: Uses organic polymers with acidic or basic groups (like sulfonic acid groups) for cation/anion exchange.
Step 1: Matching Calgon method.
Calgon is a trade name forSodium hexametaphosphate, represented by the formulaNa\(_6\)(PO\(_3\))\(_6\). Therefore,A matches with IV.
Step 2: Matching Ion exchange and Clark's method.
The Ion exchange method (Zeolite process) usesSodium aluminum silicate, formulaNaAlSiO\(_4\). Therefore,B matches with III. Clark's method specifically involves the addition ofSlaked lime, formulaCa(OH)\(_2\), to precipitate carbonates. Therefore,C matches with II.
Step 3: Matching Synthetic resin method.
Synthetic resins used for cation exchange are large organic molecules containing groups like-SO\(_3\)H (sulfonic acid groups), represented asRSO\(_3\)H. Therefore,D matches with I.
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