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Testing unknown solutions.

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Introduction

Chemistry Practical Test (Part A): Planning Exercise Testing unknown solutions Introduction In this practical investigation, I have to devise a logical sequence of chemical reactions to find out which unknown chemical goes with which name. I then have to outline a titration procedure for working out the exact concentration of aqueous nitric acid using aqueous sodium carbonate, concentration of 0.500 mol dm�� Precautions - Health and Safety * Wear safety glasses * Handle all chemicals with care * Wash hands before and after handling and chemicals * Have an eye wash available. Equipment Test tubes, Small pipette, Calcium carbonate (marble chips), Dilute hydrochloric acid, Silver nitrate, Nitric acid, Aqueous ammonia solution, Limewater, Delivery tube and stopper, Bunsen burner, Safety mat, Test tube holder Procedure (1) ...read more.

Middle

(3) Positive test for acids: Acid + carbonate carbon dioxide + water + salt * If both of the two unknown solutions left show a positive result, they are both acids, so I only need to work out either which is the nitric or the ethanoic acid, because the last solution would be the other acid. (4) Test for ethanoic acid: Esterification - if solution is ethanoic acid, it smells like pears. * Heat gently, allow to cool, smell cautiously Alcohol + carboxylic acid ester + water Danger - adding sulphuric acid to a dilute solution means that it could react with the water - could be explosive Risk assessment of Nitric acid * Corrosive * Oxidizing agent * Dangerous with ethanoic acid - if comes ...read more.

Conclusion

* Work out mean titre (for calculation = X) Calculation Solution A - nitric acid, volume - 25.0cm�, concentration - ? Solution B - sodium carbonate, volume - X, concentration - 0.500 mol dm�� 1000cm� of solution B = 0.5 mols NaCO3 In Xcm� NaCO3 there are: 0.5X / 1000 mol From equation: NaCO3 + HNO3 1 mol NaCO3 reacts with 1 mol HNO3 Mols HNO3 present in 1000cm� = (0.5X /1000) x 1000 25 = 0.5X � 25 The concentration of the nitric acid solution is therefore 0.5X � 25 mol.dm�� Fair test, precise and reliable data > Will repeat all experiments 3 times > All experiments - room temperature > Will use accurate equipment, e.g. calibrated pipette filler > Will compare data against specimen data to check reliability. Helen Spencer, candidate number: 9326, centre number: 55245 ...read more.

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