Student Question

Explain in detail how finding the value of Ksp for a basic compound (ex. calcium hydroxide Ca(OH)2(aq)) determined by performing an acid-base titration (ex. adding calcium hydroxide drops to 10 drops of 0.050mol/L hydrochloric acid and phenolphthalein solution until the solution turns permanent pale pink) is useful including separate ideas about society, economics, and the environment.  (Does not have to include this specific example) 

Expert Answers

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Calcium hydroxide is a weak base that has an equilibrium expression of:

`Ca(OH)_2 -> Ca^(2+) + 2 OH^(-) `

The ksp expression would be:

`ksp = [Ca^(2+)][OH^(-)]^2 `

This expression is similar t most of the heavy metals that are being analyzed in the analytical laboratories. Heavy metals can do harm to people so measuring it is very necessary in order to prevent further damage to humans, animals, plants and the community. Well in the case of calcium hydroxide, it is not much of a problem compared with other metals such as mercury, cadmium and lead which can lead to extreme damage at a very minute amount. 

The first thing analytical chemists do is to precipitate the heavy metals in the sample solution so that it can be able to be determined. Finding the value of ksp of a particular species is useful so that we can be able to know the limits where the compound is going to precipitate. This detection is useful in order to see if a particular sample has exceeded a hazard limit for living organisms. 

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