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To Determine The Concentration Of Limewater Solution

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Introduction

To Determine The Concentration Of Limewater Solution In this experiment I will be determining the concentration of limewater. A titration will be carried out, which will neutralise the limewater, using hydrochloric acid. The balanced equation for this experiment is: Ca(OH)2 + ?HCL -------> CaCl2 + H2O Apparatus * ??? cm 3 Volumetric Flask } * Pipette } Used In Dilution Oh Hydrochloric Acid * 25ml 2.00 Hydrochloric Acid } * Burette * Clamp Stand * A Beaker Of 250 cm 3 Limewater With Approximately 1g dm 3 Calcium Hydroxide * A Beaker Of 250 cm 3 Hydrochloric Acid (diluted x100) * Funnel * Pipette * Conical Flask * Phenolphthalein Indicator * Distilled Water Hydrochloric Acid The concentration of hydrochloric acid is too strong, at 2.00 mol dm3 therefore it needs to be diluted. The reasoning for this is that to be used in its present form for the titration would mean only a very small amount would be needed to neutralise the limewater, which would be very difficult to measure and make the results too inaccurate. To calculate the amount needed to dilute the hydrochloric acid, first I need to find the concentration of Ca(OH)2: Ca(OH)2 = ? g dm3 Mr of Ca(OH)2 = 40+ (16 x 2 + 1 x 2) ...read more.

Middle

* Fill the flask with water, so the meniscus lies directly on the 250 cm3 mark. * Clean out the pipette with distilled water, so the more concentrated HCL is washed out. * Take 25ml now from the diluted acid in the volumetric flask using the pipette and pour into another volumetric flask (or use the same one after it has been cleaned thoroughly with distilled water) * Once again fill the flask up to the 250 cm3 mark. The HCL is now diluted x100 and ready to be used in the titration. Method Titration * Set up equipment for the titration as shown in the diagram above. * Use the pipette to measure 25ml of the limewater solution and pour it into the conical flask. * Add small amount of Phenolphthalein Indicator to the limewater, and ensure the amount added each time the experiment is repeated is consistent. * Place the clamp stand and burette on a lower surface with the funnel in the top so it is much easier and safer to pour in the Hydrochloric Acid. * Fill the burette up slowly with HCL, making sure you are eye level so you can see clearly when the meniscus reaches the ? ...read more.

Conclusion

Volume Volume - 25 / 1000 = 0.025 0.00076 / 0.025 = 0.0304 mol/ dm3 This now needs to be converted to g dm3 so it will need to be multiplied by the Mr of Ca(OH)2: 20 + 2( 16 + 1 ) = 74 0.0304 x 74 = 2.2496 = 2.24 g dm3 I will now identify any sources of error and calculate how this would affect the final result I have obtained. I will find the total errors in the equipment I have used, for example on the burette the smallest reading you can measure is 0.05 cm3, to find the percentage error of this equipment I divide 0.05 by the titre and multiply by 100: Burette = (0.05 / 7.6 ) x 100 = 0.6578 = 0.66 % The error on both the volumetric flask and pipette is 0.125%, so to find the overall error I will add these errors and use that percentage to find the error on the final concentration of the limewater solution: 0.66 % + 0.125 % + 0.125 % = 0.91 % 2.24 / 100 = 0.0224 0.0224 x 0.91 = 0.0203 = 0.02 So my error in the final result of the concentration of limewater solution is + or - 0.02 from the final result. Sources: http://www.bsieducation.org/Education/14-19/topic-areas/applied-science/images/titration-equipment.jpg http://www.chemistry-react.org/go/Faq_24489.html http://www.creative-chemistry.org.uk/index.htm ?? ?? ?? ?? ...read more.

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