Determination of the solubility of calcium hydroxide.

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Determination of the solubility of calcium hydroxide

I have been given a sample of calcium hydroxide and have to find the solubility of the sample. When dissolved in water it forms an alkali solution so the method I will be using is an acid-alkali based titration. The acid I am using will be hydrochloric acid.


Ca(OH)   +  2HCl                                          CaCl   +  2H O


I want to use apparatus with a low percentage error to enable my results to be as accurate as possible and also use realistic measurements of the solutions that I will be using in my experiment.

Concentration of acid-

Using the balanced equation you can see that the ratio between calcium hydroxide and hydrochloric acid is 1:2. We already know the approximant concentration of Ca(OH) and the concentration of hydrochloric acid. These are 0.015 mol dm   and 0.300 mol dm   . At these concentrations the ratio is 1:20 so the hydrochloric acid will have to be diluted to 0.03 mol dm   before we can use it. This would be made by adding 25cm  of HCl (using a 25cm  pipette to measure the volume) to a 250cm  volumetric flask and then adding distilled water up to the graduation mark. Put the stopper in a tip upside down to insure the solution is mixed. Before using each piece of apparatus it should be washed with the solution that will be in it to ensure that no other solutions would be used in the experiment as this would result in unreliable results.

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Volume of acid-

I will be measuring out a certain amount of acid and the adding the alkali from the burette until I reach my end point.

10cm  or 25cm  pipette

% error on 10cm      =        (0.04/10) X 100

                        0.4 %

% error on 25cm      =        (0.06/25) X 100

                        0.24 %

I have chosen to use the 25cm  as this measurement has the lowest percentage error.


In 25cm  of acid        =         0.03dm X 25    =     0.00075 mols        =  0.000375 mols

                                  1000                          2

Average titre of ...

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