Determination of the solubility of calcium hydroxide.

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Shaun Gilchrist – Assessed Practical

Determination of the solubility

of calcium hydroxide


        I am aiming to determine the solubility of calcium hydroxide. Calcium hydroxide is an alkali and limewater is a saturated solution of it, therefore I can titrate it against an acid of whose concentration I know. Using this information I will be able to accurately estimate the concentration of the calcium hydroxide solution. I will be provided with limewater, which has an approximate concentration of 0.015 mol dm-3 and a solution of hydrochloric acid which has a known concentration of 0.3 mol dm-3. The concentration of the acid is too high so it will need to be diluted.

Material Quantities

Concentration of the acid

Hydrochloric Acid  +  Limewater  →  Calcium Chloride  +  Water

Ca(OH)2  +  2HCl  →  2CaCl  +  2H2O

        By observing the above equation I know that the calcium hydroxide reacts with the HCl in the ration 1:2, with the concentrations of the solutions at 0.015 and 0.3 mol dm-3 the ratio is 1:20 which means the reaction will take place far too fast to find an accurate end point. Therefore I am going to dilute the acid with distilled water a tenth of what it originally was to make the concentration 0.03 mol dm-3. I will make this solution by adding 25cm of HCl to a conical flask, and then add distilled water to the 250cm3 mark.

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  • 25cm3 pipette
  • Pipette filler
  • 50cm3 burette
  • Burette clamp and stand
  • Funnel
  • White tile
  • 100cm3 conical flask
  • 100cm3 beaker
  • 250cm3 volumetric flask
  • Calcium hydroxide
  • Hydrochloric acid
  • Methyl orange indicator
  • Distilled water


        I am using methyl orange as the indicator for my titration because HCl and Ca(OH)2 are both strong acids, and by following the information sheet provided I know to use either methyl orange or phenolphthalein. I have chosen to use methyl orange over phenolphthalein because the endpoint will result in a colour change to orange, which ...

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