Chemical and Ionic Equilibrium - Result Question 122

####66. The solubility product (Ksp) of Ca(OH)2 at 25C is 4.42×105. A 500mL of saturated solution of Ca(OH)2 is mixed with equal volume of 0.4MNaOH. How much Ca(OH)2 in milligrams is precipitated?

(1992,4M)

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Solution:

  1. Ksp =4S3=4.42×105

S=0.022M

mmol of Ca(OH)2 in 500mL saturated solution =11 mmol of NaOH in 500mL0.40M solution =200

Total mmol of OH=200+2×11=222

[OH]=0.222M

Solubility in presence of NaOH=Ksp[OH]2

=4.42×105(0.222)2=9×104M

mmol of Ca2+ remaining in solution =0.9 mmol of Ca(OH)2 precipitated =10.1

mg of Ca(OH)2 precipitated =10.1×7.4=747.4mg



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