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Analysis of vinegar. Comparing the concentration of different samples of vinegar.

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Introduction

Unit 1.4a Aim: analysis of vinegar Introduction: quantitative analysis can be used to determine the concentration of active ingredient in foods. In this experiment, samples of vinegar has been analysed to calculate the concentration of standard vinegar to the restaurant and take-away vinegar. The restaurant and take-away should contain less acid than the standard vinegar. The take-away should water down the vinegar. Titration is used to find the concentration of an acid. Titration means how much acid is needed to neutralise an alkali. Titration is known to be the more accurate method to find the concentration of a solution. The burette is used to deliver the second reactant to the flask and the indicator is used to detect the endpoint of the reaction. When the dark pink colour changes to colourless indicate the reaction is complete. The indicator is important as both solutions are colourless so it will be hard to figure out when the reaction is complete. Titration always occurs between one base and one acid, the acid is the vinegar and the base is the sodium hydroxide solution. Ethanoic acid is produced when ethanol reacts with oxygen, it is a weak acid which can be happen anywhere where there is bacteria. The restaurant use Ethanoic acid (vinegar) for preservative and food flavouring. The Ethanoic acid's pH = 3. ...read more.

Middle

The precise volume was recorded to the nearest 0.05cm3. * The burette was placed on a clamp and stand as well as the 25 cm3 sodium hydroxide solution. * The tap of the burette was opened to titrate with the sodium hydroxide solution while mixing it. * As soon as the indicator turned to a colourless colour, the tap was closed. The remaining volume was recorded. * The volume was repeated and recorded three times with each sample. Results: Standard: Burette reading 1 2 3 Final reading 22.95 23.15 23.65 Initial reading 0.45 0.45 0.55 Volume used (cm3) 22.50 22.70 23.10 Average volume (cm3) 22.767 Restaurant: Burette reading 1 2 3 Final reading 31.25 30.95 29.95 Initial reading 0.35 0.55 0.45 Volume used (cm3) 30.90 30.40 29.50 Average volume (cm3) 30.267 Take-away: Burette reading 1 2 3 Final reading 42.75 42.15 41.85 Initial reading 0.45 0.45 0.25 Volume used (cm3) 42.30 41.70 41.60 Average volume (cm3) 41.867 Analysis: According to the table, the take-away units have bigger volume than the standard units which shows that more vinegar is added to the take-away to titrate. The volume used for restaurant is more than the standard but less than the take-away. The standard vinegar is more acidic than the take-away and the take-away is water down. On average 22.8 cm3 of standard vinegar required 25 cm3 of sodium hydroxide solution, 30.3 cm3 of restaurant vinegar required 25 cm3 of sodium hydroxide solution and 41.9 cm3 of take-away vinegar required 25 cm3 of sodium hydroxide solution. ...read more.

Conclusion

In addition, to make sure to close the tap in a way just to allow drops of the vinegar to go through. 2. Measurement error Measurement error can occur when people doesn't take the readings from the bottom of the meniscus which create parallax error. Another error can occur while taking the reading from the burette as the reading should be rounded up to the nearest �0.05 cm3 and the pipette should be �0.06 cm3. This can be accurate most of the time in experiment but sometime it can't be completely accurate. How to improve it? The best way to improve parallax error is to take the readings at the bottom of the meniscus and try to be more accurate rather than rounding up to the nearest numbers sometimes. During titration, the pH of the alkaline solution will decrease as more acid is added. When the pH goes down to 7, the solution will be neutral. If more acid is added, the pH will continue to go down and the solution becomes acidic. Only a few drops of sodium hydroxide are needed to neutralise the reaction. Ethanoic acid is a weak acid which means it does not fully dissociate into ions in water. To make the results more accurate, the experiment should be carried out more than 3 times. Personally, I am quite satisfied with my results as I find it accurate. ?? ?? ?? ?? Ahvashta Seeburrun 1 ...read more.

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