Titration to analyse a solution of dilute sulphuric acid, and calculating the concentration of acid that it contains.
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Titration to analyse a solution of dilute sulphuric acid, and calculating the concentration of acid that it contains. Introduction/Aim: In this coursework my aim is to find out how much acid there is in a solution. I am going to use the technique of titration to analyse a solution of dilute sulphuric acid, and calculate the concentration of acid that it contains. This concentration is considerably greater than the concentration of acid in "acid rain", but the same method of analysis could be used to determine accurate values of PH for "acid rain" samples. I must find out the accurate concentration of acid, which is thought to have a concentration between 0.05 and 0.15 mol dm-3. The purpose of this experiment is to obtain an accurate concentration of sulphuric acid, which is found in solution. We are told that the sulphuric acid to be used has a concentration between 0.05 and 0.15 mol dm, but the task is to clarify the exact concentration using the method of titration. The indicators that I can use are either phenolphthalein or methyl orange this is because according to the titration curve for strong acid with strong base, the pH range for methyl orange (3.1-4.4)
> Use a pipette and a pipette filler to transfer 10.0 cm3 of the acid rain sample to a 100 cm3 conical flask. > Add 3 drops of Methyl orange indicator. > Fill burette with 0.01 mol dm-3 sodium hydroxide solution. > Make sure the burette jet is also full of solution. > Record the volume reading in the burette before starting the titration. > Add sodium hydroxide solution in small volumes to the acid rain solution in the conical flask. > Gently swirl the flask after each addition. > The Methyl orange indicator should turn from a orange to a yellow colour. > Run in the small volumes of sodium hydroxide solution until there is a colour change from yellow to orange colour in the titration mixture. > This is the end point. > Record the final burette reading. > Now calculate the volume of hydroxide solution that has been used. > The 1st attempt that is done would be a rough titration. > From this rough attempt I should now have an idea of what the end point is. > After this rough titration I will do several more titrations until I record three volumes that agree to within 0.1 cm3.
I feel it was best to have the acid placed in the burette rather than it in the conical flask, because it's easier to note the colour change from yellow to orange, than orange to yellow. I know that the errors that may have occurred during the experiment were minor and did not have a great impact on my final result, however I still feel that the main source of my error in carrying out the titration was where I had to distinguish where the indicator had changes colour. This is the reason for why I had to estimate an end point between the beginning and end point of the colour change. I used this method throughout all 3 of my titrations. If I was to ever do this experiment again I would make sure that I used a pH meter to distinguish the neutralization point. Even though by doing this it would not have a great impact on my titre, it will however make the investigation much more reliable and not subject to the choice of individual colour change. Also if I had more time to do this experiment I would do more titres rather than just 1 rough titre and three others. I would do several titres in order to compare them with one another. Ifrah Naz
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