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The Concentration Of Lime Water Plan
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| Words: 1300 | Submitted: 03-May-2006
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DescriptionThe Concentration Of Lime Water plan, explain how and under what conditions the experiment will be carried out
Objective: I am trying to find out the concentration of a limewater solution, containing 1gdm-3, by neutralising it with hydrochloric acid.
Equation: Ca(OH)2 + 2HCl  CaCl2 + 2H2O
Ratio: 1 : 2
Relative Atomic Masses: Ca = 40 O = 16 H = 1 Cl = 35.5
Before staring the experiment the hydrochloric acid must be diluted.
Make sure the burette is clean and double check by rindsing it out with ditilled water two to three times, get rid of the excess water by pouring it down the sink.
• Measure out exactly 2.00cm3 of HCl by the burette by placing the bottom of the meniscus exactly on the 2.00 mark to obtain accurate results.
• Rinse out the conical flask with distilled water two to three times and remove the excess water; fill the conical flask with 200cm3 of distilled water.
• Add the HCl to the distilled water, and now the HCl has been diluted.
The experiment will be repeated 5 times, this is to make the results as accurate as possible. It is very important to use the most appropriate equipment available for use. This is why I have chosen to use a pipette, volumetric flask and a burette, as they have an accuracy of +-0.005 cm, which should produce a suitable accuracy for my experiment. It is very important to read of the burette as accurately as possible and to make sure that the reading is taken from the bottom of the meniscus. This is why it is helpful to have a piece of white paper behind where you are trying to read on the burette, so it is clearer to see the bottom of the meniscus. It will be necessary to wash out some of the equipment when I am using it so I can repeat the titration to get concordant results. Some of the equipment will need to be washed out with a particular solution. For instance when washing out the burette you must wash it out with the hydrochloric acid solution, as if you washed it out with water it would affect the results as it would further dilute the hydrochloric acid which was going to be put in there. When running off the hydrochloric acid into the conical flask it is necessary to be very accurate, right to the last drop, so that you reach the endpoint and are not under it, or overshoot it.
Limewater solution, 250 cm3
Hydrochloric Acid, 25 cm3
Conical Flask, 250 cm3
Volumetric Flask 100cm3
Indicator methyl orange
Clamp and Stand
Choosing a suitable indicator is also important, I had to be extremely careful with this, I have chosen to use the indicator methyl orange. The limewater used will be a relatively weak base so it will be appropriate for using methyl orange, as it has an end point on the scale between 8-5. Other indicators can give wrong readings such as phenolphthalein indicator; this has an end point, which is much higher up the scale. If phenolphthalein is used the end point would be reached before the equivalence point.
To find out the percentage of an error the equation below can be used
Total Error of titre = 1%
Safety is very important and it is necessary to follow safety procedures when doing any experiment. Eye protection must be worn such as goggles, not following this safety rule may result in hazardous chemicals contacting with the skin or eyes. Long hair and objects must be tied back. Extra care should be taken because of the corrosive chemicals, which you are working around such as HCL. A lab coat should also be worn in case any spillage falls onto your clothes.
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