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Investigating the concentrations of different vinegars by titration

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Introduction

Investigating the concentrations of different vinegars by titration Background information: The definition of titration is to find out the exact concentration/amount of acid needed to neutralize a certain amount of alkaline. The number of moles equal to the concentration of the solution times its volume The concentration equals the number of moles in 1 dm3 I litre = 1 dm3 = 1000cm3 pH is a measure of how much H+ there are in a solution or in other words how concentrated it is. Acids contain hydrogen ions, the more H+ ions there are, the more acidic it is or the lower is the pH. In a strong acid, nearly all the acid molecules form ions. In a weak acid, only some of it forms ions. Arrhenius definition of an acid is any substances that ionize when dissolved in water to give H+ ion and a base is any substances that ionize when dissolved in water to give OH-ion. Bronsted- Lowery's definition of an acid is a proton donor (H+) and a base is a proton acceptor. Strong acids such as hydrogen disassociate almost completely HCl H+ + Cl- But weak such as Ethanoic acid reach dynamic equilibrium which is when the molecules split up at the same rate as the ions join back together again. ...read more.

Middle

4. Add just a few drops of Phenolphthalein which will turn the solution pink, because too much will make the test inaccurate. 5. Make sure the burette is held firmly by the burette stand and its tap closed tight, pour the acid to fill the burette up to the point 0, and make sure there are no air bubbles. Read off the meniscus at eye level by the bottom of the meniscus. 6. Add the acid into the conical flask by opening the tap on the burette a little each time while swirling the flask at the same time to mix them evenly, when the solution gets nearly colourless, just let one drop fall each time until the solution is just neutral, when it turns colourless. 7. By reading off the scale to the accuracy of 0.05cm3 on the burette, find out the exact amount of the different acids need to neutralise 25cm3 of sodium hydroxide. 8. Repeat the steps 3 times each for different vinegar, until you get 3 results within 0.1 concordant of each other for each vinegar, to get more accurate and reliable results. Safety: Hazardous chemical or procedure Type of hazard Control measure to reduce the risk Ethanoic acid (dilute) Low hazard lower concentration, small volume, eye goggles, protective gloves Sodium hydroxide (dilute) ...read more.

Conclusion

I had a few anomalies and the were all a bit too high than the rest of my results, this is probably due to the fact that I didn't close the tap of the burette in time as it was quiet hard to control, so extra amount of acid were dropped in, or I might not have read off the burette at eye level. Also I might not have got the right amount of the alkali, because it was quiet hard to use the pipette filler and get it to the exact volume, and some of the alkali might have spilled out of the pipette in the process to place it in the conical flask. There is also a possibility that the vinegars which we replaced after the original ones ran out had different concentrations as they were of different batches, so this also made a difference the my results. To improve my procedure, I could increase the volume of the alkali used, and dilute the acids more to 5%of its original strength for even more accurate results. For further investigation, to improve the reliability of my results and the validity of my conclusion, I could extent this experiment by using a wider range of acids, rather than just using vinegars. As fruits are also acids, I could use orange juice, apple juice, lemon juice etc. and I could even use soft drinks and tea for the acids. ...read more.

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