Experiment : To determine the percentage of ethanoic acid in vinegar.
Vinegar is a solution of ethanoic acid dissolved in water. The purpose of this titration is to find the percentage of this acid in the vinegar.
- Add 50 ml of vinegar to a volumetric flask using a 25 ml pipette twice.
- Make up the solution to the 250 ml mark with deionised water. This is the solution which will be used for the titration.
- Note: diluting the solution in this manner is necessary for two reasons (i) you will use less reagents this way and (ii) if an error is made measuring a dilute solution it will not have great implications for the final answer.
- Add 20 ml of 0.1 M sodium hydroxide solution to the conical flask using a pipette.
- Add two or three drops of phenolphthalein indicator, just enough to impart a pink tinge to the sodium hydroxide solution.
- Put the dilute vinegar solution in the burette.Titrate in the usual manner.
- The end-point is reached when the pink colour changes to colourless.
- Record the volume of acid used from the burette.Repeat the titration several times until two titration values agree to within 0.2 ml of each other.
Equation for titration
- Volume of acid used = 13 ml
- Factor for the acid = 1
- Molarity of the acid = ?
- Volume of base used = 20 ml
- Factor for the base = 1
- Molarity = 0.1 M
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