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Finding out how much acidthere is in a solution

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Introduction

Finding out how much acid there is in a solution Plan In order to find the accurate concentration of the sulphuric acid, the molarity of the acid will be determined using a titration, the process of the gradual addition of a solution of known concentration to a second solution until the solute in the second solution has completely reacted. The neutralisation reaction between sulphuric acid and sodium carbonate will be used in order to find out the concentration of the acid. H2SO4 (aq) + Na2CO3 (aq) = Na2SO4 (aq) + H2O (l) + CO2 (g) The reactants react in a 1:1 mole ratio and so as we know that the sulphuric acid is of a concentration between 0.05 and 0.15 mol dm-3, therefore sodium carbonate of a similar concentration will be needed to neutralise the sulphuric acid. Firstly an aqueous sodium carbonate solution must be made. As the solution should be approximately 0.1 mol dm-3, 0.1 moles should be weighed out to mix with 1000cm3 or 0.025 moles with 250cm3 Apparatus Sodium carbonate Weighing bottle/top pan balance Sulphuric acid (250cm3) Distilled water 250cm3 volumetric flask 100cm3 conical flask Burette Burette clamp and stand 100cm3 beaker x2 25cm3 pipette 1cm3 pipette Pipette filler Small funnel 1 White tile Spatula Stirring Rod Making the solution Mass of sodium carbonate = (23x2) ...read more.

Middle

and a weak alkali (sodium carbonate) This is therefore approprite for the experiment I am doing. Before the titration can take place the apparatus must be set up. Before the burette can be clamped in place it is important that it it rinsed through with sulphuric acid to ensure that any chemicals remaining in the burette are disposedof and so there is no contamination which may affect the results. This is best done by placing a small amount of sulphuric acid and tilting and rotating the buret as to rinse out the entire inside wall and allowing some of the acid to run through the buret tip. Clamp the burette to the clamp and fill it up with sulphuric acid past the zero mark, and slowly open the burette tap until the bottom of the sulphuric acid meniscus is on the zero mark allowing the acid to flow through the tap and place the conical flask containing the sodium carbonate underneath on top of a white tile, this tile will help colour changes to be seen more clearly. The acid can now start to be added to the conical flask in small amounts at a time, swirling the flask after each addition. ...read more.

Conclusion

x 100 = 0.16% Uncertainty using balance = (0.008/2.56) x 100 = 0.31% Uncertainty using volumetric flask = (0.2/250) x 100 = 0.08% Uncertainty using burette = (0.08/23.45) x 100 = 0.34% Finding the percentage of uncertainty of each stage of the experiment allows me to calculate the total percentage uncertainty of the experiment Total percentage uncertainty = 0.16 + 0.31 + 0.08 + 0.34 = 0.89% Calculating the concentration of the acid H2SO4 (aq) + Na2CO3 (aq) = Na2SO4 (aq) + H2O (l) + CO2 (g) Since sodium carbonate and sulphuric acid react in a 1:1 mole ratio - Moles of H2SO4 = moles of Na2CO3 Conc. H2SO4 x Vol. H2SO4 = Conc. Na2CO3 x Vol. Na2CO3 Therefore Conc. H2SO4 = Conc. Na2CO3 x Vol. Na2CO3 / Vol. H2SO4 = 1 x 25 / 23.45 = 1.06 moldmcm-3 As the overall uncertanty of the experiment was 0.89 I can say that the absolute uncertanty is 1.06 x 0.0089 = 0.009 therefore - concentration of H2SO4 = 1.06 +/- 0.009 mol dm-3 Sources 1) 'Experimental error and error analysis' - Chemical Review Magazine - Nov'01 - by Alasdair Thorpe Maria Sideras ...read more.

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