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Deducing the quantity of acid in a solution

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Introduction

Deducing the quantity of acid in a solution INTRODUCTION: To find the accurate concentration of a solution of sulphuric acid of which concentration is known to be between 0.05 and 0.15moldm-3, using solid anhydrous sodium carbonate and a range of indicators. I have to decide which indicator is most appropriate to use, then plan and carry out an experiment to determine the accurate concentration of the sulphuric acid. BASIC PLAN: * I will make a standard solution of sodium carbonate from the anhydrous sodium carbonate and calculate its concentration. * After making the sodium carbonate solution of known concentration, I will use it to determine the concentration of the sulphuric acid. This will be possible through an acid/ alkali titration. Sodium hydroxide (the alkali), will neutralise the acid in the reaction to produce a salt (Sodium Sulphate - Na2SO4) water and carbon dioxide. Add the acid until solution is neutral (the alkali has been used up), then take a measurement to find out how much acid was needed to neutralise the solution, and then can work out how much acid was needed for neutralisation. I can then use this information to find out the concentration of the acid. MAKING A STANDARD SOLUTION OF SODIUM CARBONATE APPARATUS: * Safety goggles * Spatula * Solid anhydrous sodium carbonate * A balance with a 0.01g accuracy * 2 x 250cm3 beaker * Wash bottle of distilled water * Glass rod * 250cm3 Volumetric flask with stopper and label Plan 1. ...read more.

Middle

and fill it with same solution so that the bottom of the meniscus is level with the 0 mark. 2. I will rinse the pipette with some solution of sodium carbonate and carefully transfer 25.0cm3 of the solution into a clean 250cm3 conical flask. 3. I will add 2-3 drops of methyl orange indicator solution 4. I will run the sulphuric acid solution from the burette into the flask, with swirling until the solution just turns yellow. This will be used as a trial run as I will probably overshoot the equivalence point. I will record the final burette reading to the nearest 0.05cm3. 5. I will then refill the burette with sulphuric acid to the 0 mark. 6. Using the pipette, I will transfer 25.0cm of the sodium carbonate into another clean conical flask, adding 2-3 drops of the methyl orange indicator solution. 7. Carefully, I will titrate this solution to the end point, adding the acid drop by drop when the colour is about to change. 8. I will repeat steps 5 - 7 at least twice more and keep flasks for comparison, my equivalence point should get more accurate with each repeat. Results Run Start Titre (T1) End Titre (T2) Volume H2SO4 used (titre)/cm3 Rough 0.00 20.00 20.00 1 19.95 40.30 20.25 2 2.90 23.15 20.25 3 3.90 24.15 20.25 4 0.00 20.25 20.25 CALCULATIONS: Using the data obtained from the titration, I will calculate the concentration of the sulphuric acid. Knowing most accurate titre, volume and concentration of the sodium carbonate, I will calculate the number of moles of sodium hydroxide and use ...read more.

Conclusion

The substances that will increase the value of the titre will make my result higher and the substances that will reduce the value of the titre will make my result lower. * The conical flask needs to be thoroughly rinsed with distilled water in between titrations. This will remove any solution from the previous titration and not affect the concentration of the solution in which it is to contain, as the concentration of the solution is already known. The mass of sodium carbonate (between 1.33-3.98g) I used in making the standard solution of sodium carbonate was ideal because it was calculated theoretically taking into consideration the given concentration of sulphuric acid (between 0.05-0.15mol/dm3). The volume of sodium carbonate used in the titration (25cm3) was appropriate because using a 25cm3 pipette gives more accurate and reliable result than using a pipette with a greater volume capacity. Using a pipette of volume less than 25cm3 would not make available enough solution for the titration and I would be working with very small values that can cause errors. The 25cm3 pipette I used is not too small or too big, it is just reliable. Moreover, this is used in most standard titrations. Making the solution of sodium carbonate to a volume of 250cm3 in a volumetric flask made available enough solution in case I overshoot pass the end-point and need to repeat the titration. This also ensures that there is enough solution to repeat titrations so that different values of titre will be collected and the average of them taken. This ensures accuracy. 01/05/2007 Deducing the quantity of acid in a solution Page 1 Matthew Stone ...read more.

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