Testing Vinegar – Acid Base Titration

Science C.A.T Year 9 2014 Advanced by Sara Hamilton 9H
Testing Vinegar – Acid Base Titration

Aim

The aim of this practical experiment was to pair up and measure the concentration of the acid in three different brands of vinegar. We added a base liquid, to the three different brands of vinegar until a neutralization reaction occurred. We conducted the experiment using the titration method.

Hypothesis

My hypothesis is that the vinegar that will have the highest acidic level will be Cornwell’s because it is known for being free from artificial colours, flavours and preservatives.

Materials

Burette
Stand
Beaker
Funnel
Pipette
Three different brands of vinegar
Sodium Hydroxide
Phenolphthalein Indicator
Safety Glasses

Method

1. Put on safety glasses and gather all materials needed.
2. Ask a teacher to pour Sodium Hydroxide into your burette. Make sure the initial reading is at 0mL
3. Using a pipette, measure 5mL of the brand of vinegar you will be testing and pour it into your beaker.
4. Add three drops of Phenolphthalein Indicator to the vinegar. This will indicate the colour change.
5. Slowly open the tap to the burette and drop by drop, add the Sodium Hydroxide to your vinegar, slowly swirling it as you go.
6. Continue adding the Sodium Hydroxide until a colour change occurs. Turn the tap closed and record the burettes reading of how much Sodium Hydroxide you used.
7. Repeat steps 1-7, three times for each of the three brands of vinegar.
8. Once you have recorded each brand of vinegar, clean up your work area and put away the materials.

Discussion

Define a neutralization reaction and include the word equation for the reaction performed in this CAT.

Neutralization is when a chemical reaction occurs as an acid and a base interact, which then forms salt and water.

Vinegar (acetic acid) + Sodium Hydroxide = water + salt.

Identify the acid and base in the experiment.

The acids in this experiment were the three brands of vinegar, the Coles brand, the Corn Wells brand and the Home Brand. The base in this experiment was the Sodium Hydroxide.

Identify the products and reactants in the experiment.

The reactants in the experiment would be the vinegar and the Sodium Hydroxide since those are what we are starting off with. The products are the substances that are created by the reactants, so in this case the salt and water.

Identify the most dilute and the most concentrated brand of vinegar. Justify your answer in terms of the amount of hydrogen ions in the solution.

The most dilute vinegar would be the Coles brand vinegar and the most concentrated would be the Home brand vinegar.
From the test results, the Coles brand vinegar had less hydrogen atoms, since it only took 18mL of S/Hydroxide for the solution to have a colour change occur. While the Home brand had to take 32.9mL of S/Hydroxide for it’s colour change to occur. Meaning that the Home brand vinegar had more hydrogen atoms in the solution than the Coles brand.

Explain why it was important to test each brand of vinegar three times.

The reason why it was important to test each brand of vinegar three times was to require an average of how much Sodium Hydroxide was to be added to the vinegar for it too change colour. The three tests prove that only completing one test does not give an accurate reading.

Outline how the practical could be redesigned / changed to reduce possible errors

The only problem that occurred when doing the practical experiment was that if the burette was too small, then the readings wouldn’t be as accurate since the Sodium Hydroxide would run out, which would needed to be filled again, wasting time if you are only on the first or second test.
Having each burette the same large size would give everyone a more accurate reading to everyone else and would reduce wasting time and getting inaccurate readings.

Conclusion

In conclusion, the vinegar that was the strongest was the Home Brand vinegar, having required an average of 32.9mL for a colour change to occur in the vinegar.
The weakest was the Coles brand vinegar, having required an average of 18mL for a colour change to occur in the vinegar.
My hypothesis wasn’t far off, since Cornwell’s was the second strongest vinegar. I didn’t really think much of the Home brand vinegar because I didn’t really know whether or not it would be acidic since it didn’t come from a well know brand.