Presentation is loading. Please wait.

Presentation is loading. Please wait.

+ Titrations Noadswood Science, 2013. + To know what titrations are and how these are useful Thursday, February 04, 2016 Titrations.

Similar presentations


Presentation on theme: "+ Titrations Noadswood Science, 2013. + To know what titrations are and how these are useful Thursday, February 04, 2016 Titrations."— Presentation transcript:

1 + Titrations Noadswood Science, 2013

2 + To know what titrations are and how these are useful Thursday, February 04, 2016 Titrations

3 + For some synthesised chemical compounds it is very important that they have a high level of purity (just a tiny amount of an impurity in a drug could cause a great deal of harm to a patient) Samples of chemicals that are synthesised must be checked for purity – this is often done by carrying out a titration A titration is used to measure the volume of one solution that exactly reacts with another solution…

4 + Observation Your task today will be to carry out a titration, and record accurately your results… You will need to follow the instructions carefully and ensure you record everything as you go along It is crucial your measurements are correct – remember we are looking to see the purity which is crucial in many industries

5 + Titration Titrations are extremely accurate ways of finding out exactly how much of one chemical is needed to react with another Concentrations can also be calculated from the results of a titration (knowing the balanced chemical equation) An analyst adds a measured volume of one solution to a flask using a pipette (usually 25ml) A standard solution is added from a burette An end point is determined by an indicator of pH meter

6 + Rough Titration Clamp a 50cm 3 burette in a stand and use a funnel to fill it with dilute nitric acid Use a pipette and safety filler to measure 25cm 3 dilute ammonium hydroxide (ammonia solution) Add 100cm 3 alkali to the conical flask Add a few drops of methyl orange indicator to the alkali in the conical flask – the solution will turn orange Add nitric acid from the burette to the conical flask slowly – stop it is soon as it changes from orange to red – record the volume of ammonium hydroxide added

7 + Fine Titration Repeat the experiment with clean glassware, but this time stop the titration 1cm 3 before the end of the previous volume you reached This time complete the titration, adding 1x drop at a time and swirling the conical flask as each drop is added until the indicator permanently changes colour from orange to red Repeat another fine until you have 2x results within +/- 0.1cm 3 of each other

8 + Evaporation Finally repeat the titration without any indicator, and stop at the know finish point Transfer the solution into an evaporating basin, and evaporate off the water (leaving the ammonium nitrate salt behind)

9 + Calculations Nitric acid + Ammonium hydroxide  Ammonium nitrate + Water HNO 3 + NH 4 OH  NH 4 NO 3 + H 2 O ∴ Ammonium nitrate produced should be 80g ((N x 14) x 2); ((H x 1) x 4); ((O x 16) x 3)

10 + Calculations The theoretical yield of this experiment would be 80g in every 1000cm 3 (which is 2g for our 25cm 3 ammonium hydroxide used) Theoretical yield = 2g Actual yield = 1.45g Percentage yield = (actual yield ÷ theoretical yield) x 100 Percentage yield = 72.5%

11 + Calculations How can concentration be measured? Concentration is a measure of how many things there are in a given space, measured in moles per dm 3 1 litre = 1000cm 3 = 1dm 3

12 + Concentration – Moles per dm 3 Concentration = number of moles ÷ volume *Volume in dm 3 c n V n = number of moles c = concentration (mol/dm 3 ) V = volume (dm 3 )

13 + Concentration – Grams per dm 3 Mass = number of moles x relative formula mass n m MrMr m = mass(g) n = number of moles M r = relative formula mass


Download ppt "+ Titrations Noadswood Science, 2013. + To know what titrations are and how these are useful Thursday, February 04, 2016 Titrations."

Similar presentations


Ads by Google