Aim: I have been asked to find out if any of the suppliers have been watering down the vinegar they have supplied to the chip shop owner. I will do this by using a technique called Titration. Vinegar is ethonoic acid What is Titration? Titration is a form of neutralisation. This is a process of determining the concentration of a substance in solution. A measured amount of a known solution concentration (molarity) is added to an unknown volume of a second solution in carefully measured amounts until a reaction of definite and known proportion is completed.
Neutralisation is when a Hydrogen ion and a Hydroxide ion react together to form water which is neutral. Variables: Amount of acid (vinegar) Sample of Vinegar I will be changing the vinegar samples as I will be testing shop A, B, C and Safe Way. The amount of alkali will change because the vinegars may have different molarities. Apparatus: An Acid An Alkali A Burette A conical flask A stand and a clamp A beaker A Pipette An Indicator (methyl orange) . Theory:
Whichever vinegar needs the most alkali to neutralise the acid has been watered down, once this has been done the results have to be calculated into the same units, I will be using moles (M). the difference between the molarity of the acids can tell me which has been watered down the most. Prediction: The acid with the lowest molarity has been watered down, but unless I test pure ethonoic acid, or find out its molarity then I dont know if the highest molarity of acid has been watered down. Diagram: Method: Step 1: Wash out all equipment. Step 2: Set up the stand and fit the burette in place with the clamp above the conical flask.
Step 3: Take out the burette and fill with sodium carbonate. Step 4: Measure the first acid (shop A) in the pipette then put into beaker underneath, then take the conical flask from under the burette and pure in acid. Step 5: Dilute the acid with pure H2O so there is a higher volume to work with Step 6: Start the titration by turning the tap of the burette very slightly and adding a small amount of sodium carbonate at a time. Step 7: Record results in a table.
Step 8: Repeat the experiment so you have two sets of results Step 9: Repeat all steps with the other acids Test results: A Na2CO3 = sodium carbonate CH3COOH = ethonoic acid Equation for the reaction of neutralisation with ethonoic acid and sodium carbonate: 2 CH3COOH + Na2CO3 i?? 2CH3COONa + CO2 + H2O This equation shows that; 2 moles CH3COOH = 1 mole Na2CO3 So to work out the molarity of each acid I need to use the equation below: (V = volume M = molarity).
The acid with the lowest molarity has been watered down. I know this because it took less alkali to neutralise it. Shop B, Safe Way and Shop C have obviously been watered down because they have a lower molarity than shop A. So the chip shop owner should only buy shop A vinegar as it is the strongest and he is getting more vinegar for his money.
Evaluation: To ensure my experiment was a fair test I had to make sure all the variables were the same. I made sure the factors, which needed to be constant, were constant, for example the volume of vinegar was measured accurately. I also made sure any human errors such as not switching the tap off in time were to the best of my ability. This made the experiment a fair test. These are important factors because it can be detrimental to how accurate my results are. The test was a success because we found out which was the strongest vinegar for the chip shop owner to buy.