Chemistry Cwk Concentrations: Who's cheating on the vinegar?

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Who’s cheating on the Vinegar?

I will be investigating the concentrations of ethanoic acid in 6 different samples of diluted vinegar using the process of titration.  

I will use the following apparatus and chemicals:

  • Burette
  • Clamp stand
  • 6-12 Conical flasks
  • Measuring Cylinder
  • White Tile
  • Goggles
  • Lab Coat
  • Funnel
  • 6 different concentrations of ethanoic acid solution (vinegar)
  • Sodium Hydroxide
  • Phenolphthalein  

Firstly, I will set up the burette and the clamp stand and fill the burette with Sodium Hydroxide to the zero mark. I will then measure out 20cm³ of one of the ethanoic acid solutions, using a measuring cylinder, and place the vinegar into a conical flask. Next, I will add three drops of phenolphthalein indicator to the vinegar solution and position the flask under the burette. Gradually, I will release small quantities of the Sodium Hydroxide into the solution until the liquid turns a pale but distinct pink, indicating that the solution has been neutralised.

After recording the volume of sodium hydroxide required to neutralise the acid, I will repeat the experiment for the same vinegar so as to calculate an average. I will then perform the experiment again for the remaining vinegar concentrations, acquiring two results for each vinegar. From the averages of these results, I can then calculate the concentrations of ethanoic acid in each of the solutions using chemical formulae and my knowledge of the reaction.

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My prediction is that the solution which requires the most sodium hydroxide to neutralise it will have the highest concentration of ethanoic acid. This is because if there is a greater concentration of ethanoic acid, there is a greater amount of it. A larger volume of ethanoic acid will require a larger amount of sodium hydroxide to neutralise the full quantity. In this chemical reaction, the ratio of ethanoic acid to sodium hydroxide is 1:1, so for the solution to be perfectly neutralised an equal amount of both chemicals is required.

The following results ...

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The author uses spelling, grammar and punctuation correctly, and uses scientific language to improve his work. Their communication is good and makes their piece easy to understand.

The author clearly explains the purpose of the experiment, and calculates the concentrations of the acids by using various formulae, however they could go into a lot more depth than they do. In the tables produced they fail to give the units of the measurements, making them less useful than they would otherwise be. The formulae given are correct for their experiment (or so I assume, though as there are no units on the tables, they might not be) but could be given in their more general forms and then turned into the ones required for the experiment. This would make their coursework easier to understand because the equations would be better derived. The author also mentions that ethanoic acid reacts with sodium hydroxide in a one to one ratio, which is true and a useful and important point. To improve their coursework the author could have given the equation for the reaction to show how they knew the ratio was one to one. The author talks about how they would improve their results, but does not mention using a more accurate measuring cylinder, or doing more repeats. The author could also have drawn a graph of their results, and could have created a test solution with a known concentration of ethanoic acid to check the accuracy of their results.

The author asks “Who’s cheating on the vinegar?” but fails to explain what they mean by this, and thus to answer their own question, my suggestion would be to use a boring but simple coursework title such as “Which of samples A to F is the most concentrated?”. However, as a piece of coursework it does explain how to conduct the experiment mentioned, and manipulates results accurately.