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To find out the molarity of the acid using 25cm3 of acid to neutralise 0.10 mole of alkali

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Introduction

Chemistry Coursework To find out the molarity of the acid using 25cm3 of acid to neutralise 0.10 mole of alkali Analysis We used a pipette to measure the acid and this was a measurement of 25cm3. A burette was used to measure the alkali, along with methyl orange as an indicator because this has a pH range of 3-7. We did the experiment 5 times to get a range of results. 1 2 3 4 5 Ending reading (cm3) 29.20 28.80 28.60 28.85 28.75 Starting reading (cm3) 0.00 0.00 0.00 0.00 0.00 Volume of alkali used (cm3) 29.20 28.80 28.60 28.85 28.75 Volume of acid used (cm3) 25.00 25.00 25.00 25.00 25.00 When doing an experiment the apparatus can have a error or you could actual read it wrong. Referring to "Nuffield Advanced Chemistry" as my secondary source, pipettes and burettes have a percentage error. Pipettes have and accuracy of one drop. ...read more.

Middle

have made an accurate solution we can find out the molarity of the acid by using the average result of alkali used. The average = 28.75cm3 To get the amount of alkali used in dm3 you need to: 28.75cm3 = 0.0287dm3 1000cm3 dm-3 Then we need to: Moles = 0.100mol dm-3 x 0.0286dm3 To get the moles of alkali used in 28.75cm3 So this can be shown as: Moles = 0.0028moles = 0.0028 moles of acid 1 : 1 Now that we have the molarity of the acid in 28.75cm3 We need to find the molarity of acid in 25.00cm3 So molarity of acid = 0.0028 moles in 25.00cm3 = 1000cm3 dm-3 = 40 25 To get the amount of times 25.00cm3 goes into a litre. = 40 x 0.0028 moles = 0.112 mole dm-3 This gives you the exact molarity of the acid in dm3. From this we can see that the acid was a slightly stronger molarity. ...read more.

Conclusion

Finding the end point for the pH is very difficult so instead of using methyl orange by using a digital pH meter it will be more accurate and have a less error margin. Finally by keeping each set of results and comparing the acid colours you can keep the colour constant. Instead of using a pipette to measure the acid a burette could have been used instead as it has a smaller percentage error: pipette = 0.200% and the burette = 0.175%. This would help improve accuracy. Also, if repetitions were increased then it would lead to an increase in accuracy because more results give a more accurate mean. Overall, there are 3 results within the error boundary. The 3 results are 28.75, 28.85 and 28.80cm3, and there mean is 28.80cm3. They all can have a reading mistake of 0.05cm3. So to work out the percentage error of these three results you need to: 0.05cm3 X 100 = 0.174% 28.80cm3 They are 0.174% within each other which is well within the measurement accuracy of 0.375%. Therefore the titration for the three results was done accurately. ...read more.

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