Equilibrium - Result Question 70

####74. The Ksp of Ag2CrO4,AgCl,AgBr and AgI are respectively, 1.1×1012,1.8×1010, 5.0×1013,8.3×1017. Which one of the following salts will precipitate last if AgNO3 solution is added to the solution containing equal moles of NaCl,NaBr,NaI and Na2CrO4 ? [2015]

(a) AgCl

(b) AgBr

(c) Ag2CrO4

(d) AgI

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Solution:

  1. (c) Ag2CrO4

Ksp=[Ag+]2[CrO42]=1.1×1012

[Ag+]=1.1×1012[CrO42]

AgCl

Ksp=[Ag+][Cl]=1.8×1010

[Ag+]=1.8×1010[Cl]

AgBr

Ksp=[Ag+][Br]=5.0×1013

[Ag+]=5.3×1013[Br]

AgI

Ksp=[Ag+][I]=8.3×1017

[Ag+]=8.3×1017[I]

If we take [CrO42]=[Cl]=[Br]=[I]=1

then maximum [Ag+]will be required in case of Ag2CrO4.



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