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# To determine the percentage of hydrochloric acid in a sample of diluted concrete cleaner.

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Introduction

Experiment 3b: Analysis of Concrete Cleaner Aim: To determine the percentage of hydrochloric acid in a sample of diluted concrete cleaner. Method: (Refer to sheet) Results: Concrete Cleaner Information: HCl: 33% (w/v) Density: 1.16g Weight of clean dry volumetric flask: 86.6g Weight of volumetric flask + sample of concrete cleaner: 92.8g Mass of concrete cleaner: 6.2g The aliquot used in the experiment was 'Bottle B' Sodium Carbonate. It contained 21.32g of Sodium Carbonate dissolved in 2L of solution. Titration Results: Titration number: Reading off burette before titration: Reading off burette after titration: Amount of Sodium Carbonate solution titred: 1 0.15mL 21.75mL 21.60mL 2 21.75mL 42.30mL 20.55mL 3 0.10mL 20.75mL 20.65mL 4 20.75mL 41.32mL 20.57mL The 2nd 3rd and 4th titres are concordant and will be used in the calculations. ...read more.

Middle

Therefore the mass of HCl = 92.8g - 86.6g = 6.2g 3) The average volume of the concordant titres would be; 20.55mL + 20.65mL +20.57mL = 20.77mL 3 5) The equation for the reaction that occurred between the hydrochloric acid and the sodium carbonate is: 2HCl (aq) + Na CO (aq) --> 2NaCl (aq) + H O (l) + CO (g) 4) The sodium carbonate in bottle B contained 21.23g of sodium carbonate dissolved in a solution. Therefore using stoichiometry the amount of sodium carbonate in mol present in each conical flask can be found. 6) Using the amount of mol in sodium carbonate, stoichiometry can be employed to determine the expected mol of hydrochloric acid present in the average titre. ...read more.

Conclusion

is sodium carbonate was added then molarity calculations would be higher than should be. The pipette should be rinsed with sodium carbonate alone because if water was used then the sodium carbonate would be more diluted and more solution would be needed in the titre and therefore the result would once again be affected. The conical flasks should be rinsed with de-ionized water. This is because de-ionized water will be added in the flask anyway so as long as the number of mol are calculated before the sodium carbonate is put in the conical flask. Conclusion: The percentage of hydrochloric acid in a sample of diluted concrete cleaner was found to be 28.3%. The reason for the difference of 4.7% could be that every time the concrete cleaner is opened, hydrochloric acid gas is lost and therefore loosing concentration. ...read more.

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