Chemical and Ionic Equilibrium - Result Question 113

####57. (a) Find the solubility product of a saturated solution of Ag2CrO4 in water at 298K if the emf of the cell AgAg+(saturated. Ag2CrO4 solution.) |Ag+(0.1M)Ag is 0.164V at 298K.

(1998, 6M)

(b) What will be the resultant pH when 200mL of an aqueous solution of HCl(pH=2.0) is mixed with 300mL of an aqueous solution of NaOH(pH=12.0) ?

(1998,6M)

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Solution:

  1. (a) E=0.164=0.059log[Ag+]anode 0.10

[Ag+]anode =1.66×104M

[CrO42]=[Ag+]2=8.3×105M Ksp =[Ag+]2[CrO42] =(1.66×104)2(8.3×105) =2.3×1012

(b) pH of HCl=2

[H+]=102M

Moles of H+ions in 200mL of 102MHCl solution

=1021000×200=2×103

Similarly, pH of NaOH=12

[H+]=1012M  or [OH]=102M [[H+][OH]=1014m]

Moles of OHion in 300mL of 102MNaOH solution

=1021000×300=3×103

Total volume of solution after mixing =500mL

Moles of OHion left in 500mL of solution

=(3×103)(2×103)=103

Molar concentration of OHions in the resulting

 solution =103500×1000=2×103M pOH=log(2×103) =log2+3log10 =0.3103=2.699 pH=142.699=11.301



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