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Permutit is:

(a) hydrated sodium aluminium silicate

(b) sodium hexa meta-phosphate

(c) sodium silicate

(d) sodium meta-aluminate

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(a) Permutit are complex inorganic salts like sodium alumino silicate Na2Al2SiO3·xH2O or zeolite (Na2Z) where Z is Al2SiO3·xH2O

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When zeolites, (hydrated sodium aluminium silicate) is treated with hard water, the sodium ions are exchanged with:

(a) H+ ion

(b) Ca2+ ion

(c) SO42- ion

(d) OH- ion

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(b) Na2Z + Ca2+            CaZ + 2Na+

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Temporary hardness is caused due to the presence of:

(a) CaSO4

(b) CaCl2

(c) CaCO3

(d) Ca(HCO3)2

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(d) Bicarbonates of Ca and Mg are responsible for temporary hardness.

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1000 g aqueous solution of CaCO3 contains 10g of calcium carbonate. Hardness of the solution is:

(a) 10 ppm

(b) 100 pm

(c) 1000 ppm

(d) 10000 ppm

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(d) Hardness is expressed in g of CaCO3 present in 106g of H2O.

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Which method cannot be used to remove hardness of water ?

(a) Clark's method

(b) By adding washing soda

(c) Calgon process

(d) Filtration

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(d) The ions responsible for hard water are soluble in water.

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Which salt does not cause hardness of water ?

(1) Mg(HCO3)2

(2) CaCl2

(3) MgSO4

(4) MgCO3

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(4) MgCO3 does not cause hardness of water.

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Chemical A is used for water softening to remove temporary hardness. A reacts with sodium carbonate to generate caustic soda. When CO2 is bubbled through a solution of A, it turns cloudy. What is the chemical formula of A-

(A) CaCO3                             

(B) CaO

(C) CaOH2                           

(D) CaHCO32

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(C). CaOH2 is used for the softening of temporary hard water.

        CaOH2aq+CO2g           CaCO3s+H2Ol

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Polyphosphates are used as water softening agents because they –

(A) form soluble complexes with anionic species

(B) precipitate anionic species

(C) form soluble complexes with cationic species

(D) precipitate cationic species

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(C).  Sodium hexametaphosphate-a polyphosphate, combines with cations i.e., Ca2+, Mg2+ to

        form soluble complexes.

            2Ca2++Na2Na4PO364Na++Na2Ca2PO36                                                              complex soluble

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Permanent hardness of water can be removed, by adding –

(A) Sodalime

(B) Sodiumbicarbonate

(C) Washing soda

(D) Sodium chloride

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(C).  Washing soda removes both the temporary and permanent hardness by converting soluble

        calcium and magnesium compounds into insoluble carbonates. 

                     CaCl2+Na2CO3          CaCO3+2NaCl             CaSO4+Na2CO3            CaCO3+Na2SO4             CaHCO32+Na2CO3            CaCO3+2NaHCO3

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Hardness of water is due to presence of salts of –

(A) Na+ and K+                                  

(B) Ca2+ and Mg2+

(C) Ca2+ and K+                                 

(D) Ca2+ and Na+

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(B).   Hardness of water is due to the presence of bicarbonates, chlorides and sulphates of Ca and

         Mg on it. These Ca2+ and Mg2+ ions react with the anions of fatty acids present in soaps to

         form curdy white precipitates. As a result, hard water does not produce lather with soap

         immediately. 

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