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S2/3 Chemistry. Titrations. Learning Intentions. We are learning how to carry out an accurate acid/base neutralisation reaction, using a titration technique.
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S2/3 Chemistry Titrations
Learning Intentions • We are learning how to carry out an accurate acid/base neutralisation reaction, using a titration technique. • We are learning how to complete a volumetric titration calculation, which will allow unknown concentration of either an acid or an alkali to be calculated.
Success Criteria • I can carry out an acid/base titration accurately. • I can accurately dilute an acid/alkali. • I can complete a volumetric titration calculation.
Titration • When an acid and alkali react together, a salt and water are formed.
Titration • When an acid and alkali react together, a salt and water are formed. • It is possible to find out exactly how much alkali is needed to neutralise an acid by carrying out a titration.
Titration Equipment burette
Titration Equipment burette pipette
Titration Equipment burette pipette alkali acid
Titration Equipment burette Conical flask pipette alkali acid
Titration Method • The pipette is used to accurately measure 25ml of alkali
Titration Method • The pipette is used to accurately measure 25ml of alkali • The alkali is placed in the conical flask and five drops of indicator are added.
Titration Method • The pipette is used to accurately measure 25ml of 0.1 mol/l alkali • The alkali is placed in the conical flask and five drops of indicator are added. • Acid is added to the conical flask carefully using the burette
Titration Method • The pipette is used to accurately measure 25ml of alkali • The alkali is placed in the conical flask and five drops of indicator are added. • Acid is added to the conical flask carefully using the burette • The end point is reached when the indicator changes colour
Titration Calculation The rough calculation is always discarded and an average Taken of the two remaining results.
Titration Calculation The rough calculation is always discarded and an average Taken of the two remaining results. Average acid volume 8.3ml
Titration Calculation • Titration calculations always start with a balanced equation
Titration Calculation • Titration calculations always start with a balanced equation HCl + NaOHNaCl + H2O
Titration Calculation • Titration calculations always start with a balanced equation HCl + NaOHNaCl + H2O 1 mol 1 mol 1 mol 1 mol
Titration Calculation • Calculate the moles of alkali added • N = c x v Number of moles n c v Volume in litres Concentration in mol/i
Titration Calculation • Calculate the moles of alkali added • n = c x v • n = conc of alkali x volume in litres • n = 0.1 x 0.25 • N = 0.025 moles
Titration Calculation • At the end point of the titration the number of moles of acid must equal the number of moles of alkali
Titration Calculation • Moles of alkali = 0.025 mole
Titration Calculation • Moles of alkali = 0.025 mole • Moles of acid = 0.025 moles
Titration Calculation • Calculate the concentration of the acid Number of moles n c v Volume in litres Concentration in mol/i
Titration Calculation • Calculate the concentration of the acid c = n = 0.025 = 0.12mol/l v 0.0083
Titration Calculation acid alkali PVC = PVC Power of acid Concentration of acid Volume of acid