Answer to Question #344566 in Physical Chemistry for heisa

Question

Whenever solid calcium hydroxide, Ca(OH)₂ (commonly known as lime) is present in water, it dissolves according to the equation:

Ca(OH)_2(s)   ↔  Ca²⁺_(aq)  +  2OH^-_(aq)

until the rate of the backward reaction equals the rate of the forward reaction and the solution is saturated.

A CAPE Chemistry student sought to determine the solubility product, K_sp of calcium hydroxide by titrating saturated solution of Ca(OH)₂ against standardized hydrochloric acid solution, HCl. The saturated Ca(OH)₂ solution was filtered, to remove excess solute, and 25mL aliquots were titrated against 0.10M HCl solution using bromothymol blue indicator.

1. Calculate the concentration of Calcium Hydroxide. 
2. Use the equilibrium expression for the dissolution of Ca(OH)₂ to determine the concentration of Ca²⁺ and OH^–
3. Calculate the Ksp for calcium hydroxide (state the units). 

Answer 1

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