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p -Block elements - ll — Chemistry STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceChemistryp -Block elements - ll1 Mark
MCQ
Polyphosphates are used as softening agents since
  • ✓
    They forms soluble complex with cationic species
  • B
    They forms soluble complex with anionic species
  • C
    They forms ppt with cationic species.
  • D
    They forms ppt with anionic species.
✓

Answer

Correct option: A.
They forms soluble complex with cationic species
a
Polyphosphates are used to remove calcium sulphate and magnesium sulphate impurities from water.

It forms a soluble complex with cation and removes the hardness of the water.

The reactions involved are:

$2 CaSO _4+ Na _2\left[ Na _4\left( PO _3\right)_6\right] \rightarrow Na _2\left[ Ca _2\left( PO _3\right)_6\right]+2 Na _2 SO _4$

$2 MgSO _4+ Na _2\left[ Na _4\left( PO _3\right)_6\right] \rightarrow Na _2\left[ Mg _2\left( PO _3\right)_6\right]+2 Na _2 SO _4$

Polyphosphate makes a soluble complex with $Ca ^{+2}$ and $Mg ^{+2}$ and removes the hardness of water caused by calcium sulfate and magnesium sulphate.

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