Finding the solubility of Ca(OH)2.

stir the solution in between the filtrations and clean out the other beaker with plenty of water.This should leave 300cm3 of Ca(OH)2 saturated solution which will be used in the titration experiment needed to find the concentration of the solution. Use some of the Ca(OH)2 to rinse out the conical flask and the pipette. Use some HCl to rinse out the burette.Assemble the rest of the apparatus as shown in the diagram on the last page.Pour (using a funnel) 50cm3 approx. of the HCl. Make sure this is done below eye level. Record the exact amount poured into the burette on to the results table. Measure the HCl to 2 decimal places where the 2nd decimal place in a 0 or a 5.Use a pipette to add 25cm3 of  Ca(OH)2 to the conical flask.Add the indicator to the 25cm3 of Ca(OH)2 in the conical flask. The solution should change colour from being clear to being pink. Swirl the solution to mix the indictor fully. First a rough titration needs to be done.This involves running the tap of the burette till a colour change from pink back to colourless is noticed. Stop pouring when some colour change is visible.Swirl the conical flask to mix the solutions.If the solution is colourless, record the amount of HCl left in the burette onto the table. If there is still some pink, add the HCl more slowly and keep stirring till the solution turns colourless and record the results.Now clean out all conical flask with water first and then rinse with Ca(OH)2.Refill the burette with HCl.Use the pipette to place 25cm3 of Ca(OH)2 in to the conical flask.Using the last result, run the tap of the burette so that the amount minus 2cm3 is used. (E.g. result = 25cm3, the amount poured should be 23cm3).Now swirl the conical flask till the solution is mixed well and the colour change stops.Now add the acid drop wise and keep swirling the conical flask till the indicator reaches its end point or the solution becomes neutralised.Record the volume used in the table.Cary out this experiment several times till concordant results are found. Justification The amount of Ca(OH)2 used is not important as long as the grams per cm3 is greater than the possible solubility of Ca(OH)2, which we are told is between 1 to 1.5 grams per cm3.The 25ml pipette will mean that 25ml of Ca(OH)2 will be used. This volume isn’t too small to create too large inaccuracies but not much to make it difficult when mixing the solutions in the conical flask.The 250ml conical flask allows plenty of space to mix the solutions well and not too large to make it difficult to notice the colour change.The white tile allows the user to see the colour difference more clearly reducing inaccuracies.Stirring the Ca(OH)2 using the stirring rod speeds up the dissolving process, creating a more concentrated solution which is closer to the saturation point quickly. Results Start                End                Change 0                18.70                18.70                (rough) 0                18.25                18.25                (concordant) 0                18.30                18.30                (concordant) 0                18.25                18.25                (concordant) Conclusion Ca(OH)2 + 2HCl → CaCl2 + 2H2O Errors 25ml pipette                        ±0.006ml                        0.24% Burette                                ±0.1ml                                0.4%                                 Total error percentage                0.64% Other errors are not given to us such as the accuracy of the HCl concentration. The solid may not have completely dissolved leaving a not completely saturated solution.