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KVPY2019ChemistryHydrogen

Permanent hardness of water can be removed by

Options

  1. Aheating
  2. Btreating with sodium acetate CH 3 COONa
  3. Ctreating with calcium hydrogen carbonate Ca HCO 3 2
  4. Dtreatment with sodium hexametaphosphate Na 6 P 6 O 18

Correct answer

D. treatment with sodium hexametaphosphate Na 6 P 6 O 18

Step-by-step solution

Sodium hexametaphosphate Na 6 P 4 O 18 (or Calgon) coverts Ca 2 + and Mg 2 + ions in water (which cause hardness) into a soluble complex. Na 6 P 6 O 18 ⟶ 2 Na + + Na 4 P 6 O 18 2 - Ca 2 + + Na 4 P 6 O 18 2 - ⟶ 2 Na + + CaNa 2 P 6 O 18 2 -

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