Question

Hardness of water is removed by:
A. Adding calcium hydroxide
B. Ion-exchange method
C. Both a and b
D. None of above

Answer 1

Hint: There are two kinds of hardness for example temporary hardness and Permanent hardness. Temporary hardness is because of calcium and magnesium bicarbonates. It tends to be taken out by bubbling followed by filtration. Permanent hardness is because of the presence of chlorides and sulfates of calcium and magnesium. It tends to be taken out by the expansion of washing pop and scathing pop.

Complete step by step answer:
Hardness of water can be taken out by the accompanying two strategies:
CLARK'S METHOD
In Clarks technique a determined measure of calcium hydroxide \[Ca{(OH)_2}\] is added to hard water. Because of response, insoluble carbonates are obtained which are isolated by filtration.
 \[
  Ca{(HC{O_3})_2} + Ca{(OH)_2} \to 2CaC{O_3} + 2{H_2}O \\
  Mg{(HC{O_3})_2} + Ca{(OH)_2} \to CaC{O_3} + MgC{O_3} + 2{H_2}O \\
 \]
ION EXCHANGE METHOD
In this strategy sodium zeolite is utilized as a particle exchanger. Na-zeolite is gone through the lines containing hard water. Sodium zeolite is changed over into calcium-zeolite or magnesium-zeolite. These are insoluble in water and are isolated from water by filtration
\[
  C{a^{2 + }} + N{a_2} - Zeolite \to Ca - Zeolite + 2N{a^ + } \\
  M{g^{2 + }} + N{a_2} - Zeolite \to Mg - Zeolite + 2N{a^ + } \\
 \]
Since both methods are used to remove hardness of water.

So, the correct answer is Option C.

Additional information:
Methods to remove temporary hardness:
Temporary hardness can be eliminated by bubbling and sifting the water.
Boiling : When impermanent water is bubbled, bicarbonates of calcium and magnesium decay to frame insoluble calcium and magnesium carbonates which can be handily separated off
By clark's cycle:

 \[
  CaO + {H_2}O \to Ca{(OH)_2} \\
  Ca{(HC{O_3})_2} + Ca{(OH)_2} \to 2CaC{O_3} + 2{H_2}O \\
 \]
Methods to remove permanent hardness:
Washing soft drink measure: Hard water is treated with a determined measure of washing soft drink when chlorides and sulfates of calcium and magnesium present in hard water get encouraged as insoluble calcium and magnesium carbonates which can be sifted off.
 \[
  CaC{l_2} + N{a_2}C{O_3} \to CaC{O_3} + 2NaCl \\
  MgS{O_4} + N{a_4}C{O_3} \to MgC{O_3} + N{a_2}S{O_4} \\
 \]
Calgon's technique: Sodium hexametaphosphate ( \[N{a_6}{P_6}{O_{18}}\] ), financially called 'calgon', when added to hard water, the response is as per the following:
 \[
  N{a_6}{P_6}{O_{18}} \to N{a^ + } + N{a_4}{P_6}{O_{18}}^{2 - }(M = Mg,Ca) \\
  {M^{2 + }} + N{a_4}{P_6}{O_{18}}^{2 - } \to {[N{a_2}M{P_6}{O_{18}}]^{2 - }} + 2N{a^ + } \\
 \]
The complex anion keeps the \[M{g^{2 + }}\] and \[C{a^{2 + }}\] particles in arrangement.

Note: There are various strategies to eliminate the hardness present in water. A couple of techniques to eliminate hardness from water are, Substance Process of Boiling Hard Water, Adding Slaked Lime (Clark's Process), Adding Washing Soda, Calgon Process, Particle Exchange Process, Utilizing Ion Exchange Resins