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titration of limewater

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To Determine the Concentration of a Limewater Solution by Titration Initial Apparatus 250cm3 Calcium Hydroxide, 2.00Mol dm-3 Hydrochloric Acid, Burette, Burette Stand, 25cm3 bulb Pipette, Pipette filler, Funnel, Conical Flask, 250ml beaker, 2cm3 Graduated Pipette, 100cm3 Volumetric Flask, Wash Bottle (distilled water), White tile, Methyl Orange Indicator, Safety Goggles Safety At the concentrations provided hydrochloric acid and calcium hydroxide are irritants therefore if your skin is to come into contact with either of the chemicals then you should rinse the solution off with water immediately and inform your teacher. If the chemicals should come into contact with the eyes, flood the eyes with water for as long as it takes for medical help to arrive. Methyl Orange is highly flammable and maybe toxic. You should wear protective goggles throughout this practical. Dilution 1Ca(OH)2 + 2HCl � 1CaCl2 + 2H2O To find the concentration of Calcium Hydroxide in mol dm-3 we need to use the formula: Mol dm-3 = g dm-3/ Mr So Mol dm-3 = 1 g dm-3 / 74.1 = 0.013495276653171390013495276653171 We'll round this to 0.01 Mol dm-3 to make the dilution calculation easier. ...read more.


The solution is then ready for use in the titration. We need to dilute the acid so that we get a good end point. A good end point is one that doesn't use all of the solution in the burette and one that doesn't use less than about 10cm3 of the solution in the burette. Therefore we are looking for an end point that is roughly in the middle. If the end point is unclear we will be unable to calculate an accurate concentration of the Calcium Hydroxide needed. For this titration if we place the acid in the burette and the alkali in the conical flask there will be 25cm3 of alkali meaning we will need 12.5cm3 of acid. However if we place the acid in the conical flask and the alkali in the burette we will need 50cm3 of alkali to neutralise the acid which is the same amount of solution that a burette can hold. ...read more.


* Add a couple of drops of the Methyl Orange indicator into the conical flask with the acid and place the flask under the burette on a white tile. We are using Methyl Orange because the titration is using a strong acid and a strong alkali so this will be the best indicator as it will give a good colour change. * Start running the Calcium Hydroxide from the burette into the conical flask while swirling and wait for a colour change. As it takes longer for the colour to disappear start adding the Calcium Hydroxide more slowly. However this is only a rough titration so it doesn't matter if slightly too much Calcium Hydroxide is added as this is only an appropriate value. * Record the volume of Calcium Hydroxide used (final volume) in a table of results. * Repeat the titration more accurately by adding the Calcium Hydroxide drop by drop as the end point is approached. The end point should be roughly around the same as that of the first titration. This set of results should be accurate to 2d.p. * Do this at least twice or until concordant results are found (�0.1cm3). ...read more.

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