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Investigating the concentrations of unknown acids

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Introduction

Mehjabeen khan Investigating the concentrations of unknown acids Aim To find out each of the concentrations of the hydrochloric acids in the Winchesters labelled A-E. This is going to be carries out by titrating the acid with NaOH. Equipment needed for this investigation Pipette - 25ml Burette Phenolphthalein Conical flask Beaker Funnel Pipette filler Clamp NaOH - the known acid of 0.1M HCl - the unknown concentration of acids White tile My predictions I predict that the different acid solutions of the HCl will be less than 0.1M because the Winchesters were topped up with water, which would have obviously weakened the concentration of the acid making the number of moles less than 0.1. Safety precautions when doing the experiment: * The equipment should be used carefully to prevent breakage of any glass. * The acids should be used carefully avoiding spillages and if any acid came into contact it should be rinsed with water immediately to prevent any irritation to the skin. Planning All the equipment is gathered together first and made sure that it is clean and safe to use. ...read more.

Middle

Results Acid A 1st try 2nd try 3rd try Initial reading of the NaOH (ml) 0.00 0.00 0.00 Final reading (ml) 25.30 25.35 25.45 Average result: 25.37ml Acid B 1st try 2nd try 3rd try Initial reading of the NaOH (ml) 0.00 0.00 0.00 Final reading (ml) 23.95 23.90 23.85 Average result: 23.90ml Acid C 1st try 2nd try 3rd try Initial reading of the NaOH (ml) 0.00 0.00 0.00 Final reading (ml) 22.85 22.70 22.75 Average result: 22.77ml Acid D 1st try 2nd try 3rd try Initial reading of the NaOH (ml) 0.00 0.00 0.00 Final reading (ml) 19.85 19.95 19.90 Average result: 19.90 Acid E 1st try 2nd try 3rd try Initial reading of the NaOH (ml) 0.00 0.00 0.00 Final reading (ml) 17.30 17.35 17.45 Average result: 17.37 Averages of the acids Acid A Acid B Acid C Acid D Acid E Amount of NaOH used to neutralise the HCl (ml) 25.37 23.90 22.77 19.90 17.37 Calculating the concentrations of the acids in moles: Acid A 0.1M x 25.37 - moles in titre 1000ml = 2.537 x 10 x 1000 25 =0.10 2.d.p Step by step of the calculations above There is 0.1M in a 1000ml and so in 1ml of the NaOH there are 0.1 moles, 1000 we can then find out how many moles of NaOH we used. ...read more.

Conclusion

There are no major anomalies in my results which may also show that all the tests were done carefully and each one was successful and reliable. On each time the experiment was performed, the end point at which the acid was neutralised by the alkalis was always carefully done without pouring too much of the NaOH into the flask which could have made it alkalis and turn the colour a deep pink. The easiest way I found to be able to reach that point is before the acid was about to be neutralised, small drops of the NaOH was added slowly until it turned pale pink and stayed for at least 20 seconds. I did not have any difficulty in reaching the end point and managed to create a pale pink coloured solution each time. I didn't find any major problems apart from the pipette fillers which would sometimes make air bubbles in the pipettes as it was measuring and taking the HCl. The investigation can be improved by taking further results of each concentration of the HCl to produce an even more accurate and reliable source of results. Better equipment can also be used and different kinds of equipment to see if they give accurate readings to 2 decimal places. ...read more.

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