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Ethanoic Acid Titration

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Introduction

´╗┐Concentration of Ethanoic Acid in Vinegar Date: 09/08/2012 Aim: To determine the concentration of ethanoic acid in commercial vinegar using titrations. Materials: 1x 25.0mL pipette 1x 250mL volumetric flask 1x 250mL waste beaker 1x 50.0 mL burette 1x Burette clamp 1x Pipette pump 1x Funnel 1x Retort stand 1x Small glass pipette 1x White tile 4x 100mL conical flasks Commercial vinegar Demineralised water Paper towels Phenolphthalein indicator Standard sodium hydroxide solution (0.1M) Water Method: A burette, a 25.0 mL pipette, four conical flasks, a plastic funnel, a 250mL beaker and a 250mL volumetric flask were rinsed with water. They were visually inspected for any solids. It was then rinsed twice with demineralised water. The burette, retort stand, burette clamp and a white tile were set up for the titration. The 250mL beaker was rinsed with a small amount of standard sodium hydroxide solution twice, and was then used to collect about 200mL of the solution in the beaker. The outside of a pipette was dried, and was later rinsed twice with the commercial vinegar. The commercial vinegar was diluted by pipetting 25.0mL of the vinegar into a 250mL volumetric flask. ...read more.

Middle

If the volume recorded was higher than the actual value then it is thought that more sodium hydroxide was used for the same amount of acetic acid, and then the concentration of the acetic acid is much stronger than it actually is. The same thing applies if the volume recorded was lower than the actual value, and then the concentration of the acetic acid is thought weaker than it actually is. This will give a false representation of what the actual concentration of a substance is. We also pipetted straight from a volumetric flask instead of pouring a volume of the solution into a clean, dry beaker and pipetting from that. This may have resulted in cross-contamination which will affect the titration and its endpoint. Another random error might have been a misjudgment of the colour change not only was the colour change very delicate and slow, but different people have different sensitivity to colours. Therefore the actual endpoint of the titration might have occurred before what we thought; hence more NaOH was added, thus increasing the concentration of the acetic acid than what it actually is. This will in turn give us inaccurate results in the end. ...read more.

Conclusion

To eliminate air bubbles around the stopcock of the burette, tap it; otherwise perform that step again ensuring there are no air bubbles present. The accuracy of glassware is limited, and not all volumetric glassware is created equally. Hence, another improvement to increase the chance of the class finding similar results would be to ensure that everyone uses similar equipment ? in particular, the burette. By ensuring that everyone uses a strategic approach to the swirling and inversion to give a homogenous solution, a consistent result can be produced across the class. Some procedural changes would include arranging the titration to have bigger titres (reducing errors), and using larger aliquots (reducing errors). The titration can also be repeated more times to ensure that the endpoint is more accurate and consistent. By attaching a white paper slide with a broad line to burette so that the line is vertical, as well as taking care to avoid parallax error, precise readings of the volume can be made. Conclusion: The concentration of ethanoic acid in commercial vinegar was determined by titrating vinegar with sodium hydroxide. Though the results may be subjected to human mistake, systematic errors and random errors, the findings of the titration were that the concentration of ethanoic acid in commercial vinegar was 5% m/v. ...read more.

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