Determination of the solubility of calcium hydroxide.
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Determination of the solubility of calcium hydroxide Aim 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.
> Wash out burette with distilled water and then with the HCl solution. Fill the burette with the HCl using a funnel and rush the jet through making sure no air bubbles are trapped. > Then use a pipette and pipette filler to transfer 25cm of limewater into a washed conical flask and add 3 drops of methyl orange indicator. > Place the conical on a white tile underneath the burette and record the reading on the burette ready to titrate. > Whilst swirling the conical flask add the HCl from the burette to the Ca(OH)2 . > Look for the end point, which will be a slight colour change to orange and then add drop by drop to ensure you do not go over the end point. > When the end point is reached record the volume in the burette and subtract it from the initial volume to find the titre. Record this as a rough titration and repeat the experiment adding a few drops at a time as you become near to the endpoint.
> Repeating the titration until all results are within 0.1cm3 of each other makes sure that the endpoint found is correct and accurate. > The burette readings are to 2 decimal places because this gives precise readings for the amount of titre so when calculating the concentration of the acid it will be accurate. Percentage errors Burette = 0.20% Pipette = 0.24% Flask = 0.08% Total Percentage Error = 0.52% Risk Assessment Hydrochloric Acid Corrosive and irritant. Wear eye protection and gloves. If substance gets in to eyes, mouth or on skin wash with water and seek medical attention. Calcium Hydroxide Corrosive and irritating to eyes. Wear eye protection and gloves. If hands are contaminated and the substance gets in to eyes or mouth, flood with excess water and seek medical attention. Calcium Chloride Irritant to eyes, skin and respiratory system. Is dangerous with water as it is an anhydrous salt and can cause water to boil. Wear eye protection and gloves. Use in a well ventilated area. If substance gets in to eyes, mouth or on skin then wash with water and seek medical attention.
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