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Find the concentration of limewater solution Titration

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Introduction

Finding the Concentration of Limewater Solution The aim of the experiment is to find the concentration of a limewater solution (calcium hydroxide) as accurately as possible. The limewater solution is approximately 1gdm-3 but to get a more accurate concentration I will use an acid based titration. A neutralisation reaction will take place between the acid (hydrochloric acid) and the base (calcium hydroxide) during the titration. I will use the base to neutralise the acid and make a salt (calcium chloride) and water. This reaction can be written as: 2HCl + Ca(OH)2 � CaCl2 + 2H2O However I need to find the exact concentration of the reagent, Calcium Hydroxide solution. To overcome this problem I will need to perform an acid based titration. The other problem is that the acid reagent is too concentrated as it is 2mol/dm�. This means the reaction will occur faster because there is a greater chance of a successful collision, which means it would be harder for me to acquire an accurate result, as the end point will occur too quickly. I will need to reduce the concentration of the hydrochloric acid, thus prolonging the time taken for the reaction to take place so I can get a more accurate result*. So I can make accurate calculations with my results I will need to convert the concentration of the limewater solution, which is in g/dm�, to mol/dm�. ...read more.

Middle

Slowly let the water drain out whilst twisting the burette so that it is washed from all sides. Then turn it back the right way and open the burette tap, releasing all the water from the burette. Next repeat the process using HCl to get rid of the deionised water. We now need to wash out the pipette. To do this you need the pipette filler. Place the pipette filler on top of the pipette and squeeze out the air in the filler by pressing the valve at the top of the filler, then to suck the limewater into the pipette you need to press the valve at the bottom of the filler. Fill it to approxamatly half way and repeat the process of cleaning used with the burette. Use deionised water first and then the substance going to be used, which is limewater solution. Finally the conical flask in which you will put 25cm� of Ca(OH)2 needs to be washed, but with deionised water only. You now need to set up the burette. Fix it to the clamp so that the 0 mark is roughly at eye-level. If it is too high, then you need to place it on a stool to fill the burette. You now need to fill the burette with HCl, using a funnel, to about twice the amount you need. ...read more.

Conclusion

Therefore the titre end point has an error analysis of 0.1cm�. To work out the percentage error you must divide the error analysis by the the reading taken, for example if the titre end volume is 25cm�: Percentage error = (0.05/25) x 100 = 0.4% % Error of the 5cm� pipette The pipette has an error of 0.1cm�. Therefore the percentage error is: Percentage error = (0.05/5) x 100 = 1% % Error of 25cm� pipette The pipette has an error of 0.05cm� so the percentage error is: Percentage error = (0.05/25) x 100 = 0.2% % Error of 500cm� volumetric flask The volumetric flask has an error of 0.2cm� so the percentage error is: Percentage error = (0.2/500) x 100 = 0.04% This is the reason for the equipment stated for experiment, as it has a lower % Error than a simple measuring cylinder. Also this is the reason for diluting the acid instead of using 2mol/dm�. The original acid would have given a much higher percentage error because the The total error of the equipment used in the experiment is experiment is �1.64%. From the error calculations we can determine why it is better to use diluted HCl rather than the 2mol/dm� HCl. If the full concentration is used and the titre used is 20cm� then the amount of HCl required is: 20/100 = 0.2cm� therefore the percentage error is: Percentage error = (0.1/0. ...read more.

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