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I am using 10cm3 of limewater I predict that I will use roughly the same amount to neutralise it, and therefore I think that I will use about 10cm3 of acid in each titration.

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PRELIMINARY WORK Before the main experiment I carried out some preliminary work. This was for me to decide which indicator would be suitable for the main experiment. For an indictor to be suitable the indicator needs to have- -a sharp colour change rather than gradual, no more than one drop of acid or alkali needed to give a complete colour change. -a distinct colour change -an end point of the titration the same as the equivalence point, otherwise the titration will give a wrong answer. From my preliminary work I picked two suitable indicators, phenolphthalein and methyl orange. The reason these two were the best is because they gave distinct and sharp colour changes. In the end I choose to use methyl orange. This indicator has a ph of 3.1 - 4.4, and is used in reactions involving a strong acid and a weak base. PREDICTION Because of the fact that I am using 10cm3 of limewater I predict that I will use roughly the same amount to neutralise it, and therefore I think that I will use about 10cm3 of acid in each titration. I also used my preliminary work to help me with this as I used around 20cm3 of acid when using 20cm3 of limewater. I think that my end concentration of limewater in gdm is going to be around 1.0. ...read more.


I will then fill the burette back to the top and start the experiment again. However I will try and use a new conical flask if there is one available if not I will wash it out thoroughly and then start again. I will try to do as many titrations as possible or until I get three concordant results. AIM The aim of this investigation is to find the concentration of a sample of limewater solution in gdm. Limewater is also known as Ca(OH) . It is produced by the following reactions- - strong heating of calcium carbonate produces calcium oxide and carbon dioxide. This type of reaction, where a compound is broken down by heat is known as thermal decomposition - calcium oxide reacts vigorously with water to produce calcium hydroxide (slaked lime) - further addition of water to calcium hydroxide produces a saturated aqueous solution Calcium hydroxide (limewater) is only slightly soluble in water. These compounds are often called 'sparingly soluble'. As the concentration of calcium hydroxide in limewater is low, the solution has a low concentration of hydroxide ions, OH . The ph of limewater is about 9-10. USES AND PRODUCTS OF LIMEWATER Limewater can be used to identify carbon dioxide gas. When a sample of CO is bubbled through limewater, a cloudy white precipitate forms. The precipitate is solid calcium carbonate.. This precipitate of CaCO will dissolve in excess CO to form calcium hydrogencarbonate. ...read more.


Also it is important not to inhale the indicator when opening the bottles as these can irritate the eyes and the respiratory system. Limewater is also an irritant to eyes. I will also keep all the equipment in the middle of the table as most equipment is glass so I will be careful not to break anything. ANALYSIS From my results I can see that my prediction was not absolutely correct, however I feel that it was very close. I did have an anomalous result which was my first titration. In my first titration I used 16.7cm3 of acid for the colour change. However this did not tie in with my 3 other titrations which were all concordant with each other. I believe that an average of 14.3cm3 is not as accurate as it should be, as I predicted that I would roughly use around 10cm3, because of the fact that we were using 10cm3 of limewater. My final result of 1.06 gdm was a good result as it was very near 1.0. I am happy with this result as it was very close. However I feel the reason my titrations weren't closer to 10cm3 is due to the percentage errors (0.05cm3 on burette and 0.025cm3 on pipette). I feel that the first experiment was not very accurate I was not sure when to go slowly with the titration therefore I may have added I bit to much, but after I knew where about to start adding a few drops at a time. ...read more.

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