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Investigating the Concentration of Citric Acid

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Introduction

Investigating the Concentration of Citric Acid Problem I have been set the task of determining the concentration of a sample of citric acid, using only a 1.0 M solution of sodium hydroxide and any laboratory glassware that is required. I have also been given the RMM of citric acid as 210g and I have been told that one mole of citric acid will react with 3 moles of sodium hydroxide. My Experiment Using this information I have determined that the best way to conduct this experiment is to do a titration. This will allow me to determine the amount of impure citric acid required to neutralise a known volume of 1.0 M sodium hydroxide. Consequently, by calculating the correct volume of pure citric acid that would be required to neutralise this volume of sodium hydroxide, I can calculate the percentage purity of the citric acid. Calculating the Amount of Citric Acid In order to make this experiment a good titration, I must use a reasonable amount of citric acid. This is so that the amount of citric acid needed to neutralise the sodium hydroxide is not so small that it is difficult to read off the burette, and so that it is not so large that it takes more than 50cm3, and so 2 burettes must be used. ...read more.

Middle

I will then do a trial titration to gauge the approximate amounts necessary for neutralisation to occur. I will be able to see this when the phenolphthalein indictor, which is pink in alkali, turns colourless. 5) I will then do 4 accurate titration experiments in order to ensure that my results are correct. I will then record the average value for my results. 6) I should now be able to calculate the percentage purity of the citric acid using my average value for the amount of citric acid required to neutralise the 25cm3 of sodium hydroxide. Fair Test In order to keep my experiment as accurate as possible, I will keep the amount of sodium hydroxide in the conical flask constant at 25cm3, I will also keep the concentration of the sodium hydroxide constant at 1.0 M. I will measure the amount of citric acid needed to turn the phenolphthalein colourless, and record this accurately. Safety Throughout this experiment, I will ensure that I wear safety goggles and a protective lab coat so that I my eyes and clothes are protected from the acids and alkalis and no damage is likely to be caused to either. Results Titration Results Trail Titration (cm3) Titration 1(cm3) Titration 2 (cm3) Titration 3 (cm3) Titration 4(cm3) ...read more.

Conclusion

To rectify this predicament, I could either use a larger funnel, or if this would not fit in the neck of the volumetric flask, I could control the flow of the liquid by using a large funnel above a small one. I think that the solution is particularly good as it would allow me to keep the flow of liquid constant, whilst any escaping drips would fall into the larger funnel. 3) It is also possible that my lack of experience at reading values from burettes, volumetric flasks and pipettes may give rise to minor inaccuracies. However, I would consider these inaccuracies to be extremely minor as I am fairly confident in my own ability to read off accurately. I would say, however, that my own lack of experience in using a burette and finding the exact point when the indicator changes colour may have given rise to a degree of inaccuracy. It is quite possible that I have misread the colour change on one or more occasions, or even added too many drops to allow the indicator to change colour. However, despite these minor points which could possibly give rise to some degree of inaccuracy, I am confident enough in my experimental technique to say that my results are fairly accurate within the limits of experimental error. ...read more.

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