Equilibrium - Result Question 74

####78. The values of Ksp of CaCO3 and CaC2O4 are 4.7×109 and 1.3×109 respectively at 25C. If the mixture of these two is washed with water, what is the concentration of Ca2+ ions in water?

[NEET Kar. 2013]

(a) 7.746×105M

(b) 5.831×105M

(c) 6.856×105M

(d) 3.606×105M

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Solution:

  1. (a) CaCO3Ca2+x+CO32

CaC2O4Ca2+y+C2O42y

[Ca2+]=x+y

Now, Ksp(CaCO3)=[Ca2+][CO32]

or 4.7×109=(x+y)x

similarly, Ksp(CaC2O4)=[Ca2+][C2O42]

or 1.3×109=(x+y)y

On solving, we get

[Ca2+]=7.746×105M



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