The compound which is used for removing the permanent hardness of water is_______?

The correct option is A

${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$

The explanation for the correct option:

Option(A):${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$

• Permanent hardness is known as the hardness caused due to the presence of sulfates and chlorides of calcium and magnesium in water., which cannot be removed with simple boiling.
• It is generally caused by the presence of calcium sulfate or magnesium sulfates in the water, which tends not to precipitate easily with the increased temperature.
• However,${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$ which is commonly known as washing soda mostly gets used for removing the permanent hardness of the water.

The explanation for the incorrect option:

Option(B):${\mathrm{NaHCO}}_3$

• ${\mathrm{NaHCO}}_3$is not generally used to remove the permanent hardness of the water.
• thus, the given option is the incorrect one.

Option(C):${\mathrm{Na}}_2{\mathrm{CO}}_3$

• The compound ${\mathrm{Na}}_2{\mathrm{CO}}_3$, is not mostly used in removing the permanent hardness of the water.
• Hence, the given option does not represent the correct concept.

Option(D):${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$

• ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$ is not generally used to remove the permanent hardness of the water.
• Hence, the given option does not coincide with the correct concept.

Hence, the compound which is used for removing the permanent hardness of water is ${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$ , option (A) is the correct answer.