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To determine the concentration of a limewater solution

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Introduction

AS CHEMISTRY TO DETERMINE THE CONCENTRATION OF A LIMEWATER SOLUTION PLAN The purpose of this investigation is to determine the concentration of a given amount (250 cm3) of limewater solution, which contains approximately 1 g/dm-3 of calcium hydroxide. I will also be provided with 2.00 mol/dm-3 of hydrochloric acid, however the given acid (HCl) is too concentrated and therefore will have to be diluted accordingly. The experiment I have chosen to conduct for this investigation is a Titration and my chosen indicator for this experiment is Methyl Orange. This is an "Acid-Base Titration". Background information for Limewater Quicklime (calcium oxide CaO(s)) is made by roasting limestone (calcium carbonate CaCO3), marble, or chalk in a large furnace. Carbon dioxide is forced out of the calcium carbonate, leaving the lime in the furnace. Its chief use is in making mortar. To make mortar, water is added to the lime. This "water-slaked" lime is calcium hydroxide (Ca(OH)2 (S). It forms mortar (or plaster) when mixed with sand, water, and fiber or hair. Calcium hydroxide hardens as it absorbs carbon dioxide from the air. A solution of calcium hydroxide in water is called limewater (Ca(OH)2(aq)). This is used in medicine to correct acidity, to prevent milk from curdling in large lumps, and with certain oils as a liniment for burns. ...read more.

Middle

* After which I will place the conical flask on the stand under the burette. * I will then titrate the HCl into the limewater in the conical flask until the limewater changes colour from light orange to pink/purple * When the colour changes I will stop the burette and take a reading of the burette To gain accurate and consistent results I will repeat the experiment at least three times. Fair test To keep the experiment fair and to gain accurate results I will dilute the HCl by 98% as I have stated before. To reduce errors I have chosen many accurate apparatus such as the volumetric flask, pipette and the burette all of which have error margin of �0.05 cm3, which should produce suitable and accurate results. I have chosen methyl orange as my indicator because it has an end point of ph 8-5, which will be suitable for limewater, a relatively weak base, and HCl, a strong acid. The methyl orange will show the end point when the acid and base chemicals break up and not before which would happen with phenolphthalein. Safety When conducting any experiment safety is of the utmost importance and requires everyone to follow the safety procedures carefully and correctly, ensuring everyone who handles any chemicals wears eye protection. ...read more.

Conclusion

Although I feel my results are fairly accurate there were some errors in the experiment that could not be prevented. Evaluation The apparatus and equipment that I selected for this titration were quite reliable and any errors from these instruments are small. Other errors during the experiment that I could not have prevented are the small splashes of solution in the conical flask and the pipette holding a drop or two of limewater may have affected my results although I believe these errors to be too small to be of any relevance. The errors that I believe to have a serious affect on my results are human errors on measurements; the meniscus makes it very difficult to take an accurate reading of the burette and the pipette. Another human error occurs while judging the colour change of the solution; it is virtually impossible to judge the colour change of the limewater exactly the same all three times with the human eye. This experiment can be greatly improved if a computer was used to take all the measurements and repeating the experiment more, the more the better, to get a better average titre and overall more reliable and accurate results. I feel that my results are fairly accurate and reliable and this is proven by the fact that I obtained two identical results and third was 0.1cm3 of the mark. Page 1 of 5 ...read more.

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