To calculate the concentration of acid in a sulphuric acid solution.
A titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and the precise quantity of reactant in the titration flask. A burette is used to deliver the second reactant to the flask and an indicator is used to detect the endpoint of the reaction. So a chemical reaction is set up between a known volume of a solution of unknown concentration and a known volume of a solution with a known concentration
You will need:
* Solution of ‘acid rain’ (dilute sulphuric acid)
* Sodium hydroxide solution, 0.1mol dm-3
* 250cm3 conical flask
* 10cm3 pipette and filler
* Phenolphthalein indicator.
* White tile (to help reading endpoint)
Firstly prepare your burette, your burette should be filled with 0.1mol dom-3 of the sodium hydroxide solution. When filling a burette, close the stopcock at the bottom and use a funnel. Check for air bubbles and leaks, before proceeding. To remove any air bubbles tap the side of the burette while the solution is flowing slowly. This is because if an air bubble is present during a titration the volume readings may be wrong.
Take a volume reading and record the volume of solution in a table (see fig 1). Read the bottom of the meniscus. You need to make sure your eye is at the level of meniscus, not above or below because reading from an angle, rather than straight on will result in a parallax error.
Use a pipette to transfer 10cm3 of the ‘acid rain’ sample to a 250cm3 conical flask. Add 5 drops of Phenolphthalein indicator. Use the burette to deliver small amounts of the solution to the titration flask by turning the stopcock. The indicator will change colour when the required amount for neutralisation mixes with the solution in the flask, it will become a permanent pale pink colour. This is the endpoint and should be approached...
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