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Titration. As the purpose of the titration is to determine the concentration of potassium hydroxide solution, in order to analyse this unknown solution, we must have a standard solution (hydrochloric acid) to react with the unknown solution.

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Introduction

ACCESS CHEMISTRY UNIT A Practical Assignment - Titration Introduction Titration is a laboratory method of determining the concentration of a known reactant and is also known as volumetric analysis. Two solutions are involved. One solution is measured and poured into a flask, whilst the other is poured into a burette and added drop by drop until the required reaction is completed. The purpose of titrations is usually to determine the concentration of an unknown solution whilst knowing the chemical equation for the reaction by using a known concentration of a second solution. Titrations can also be used to determine the equation for a reaction whilst the concentrations of both solutions are known. A PH indicator is usually used to determine the endpoint of the reaction, although not all reactions require an indicator as the colour change occurs in the reaction between the two solutions. As the purpose of the titration is to determine the concentration of potassium hydroxide solution, in order to analyse this unknown solution, we must have a standard solution (hydrochloric acid) ...read more.

Middle

5. When the reading was taken from the burette, the burette was placed in a wood stand and stood in the sink to lower the 50cm3 line to eye level to avoid the error or reading from the meniscus. 6. The burette was securely attached to a wood stand and placed over the conical flask. 7. The tap on the burette was opened and 10cm3 was allowed to pour into the conical flask slowly. 8. The solution was stirred again by swirling the solution in the conical flask. 9. The tap was opened again on the burette and only one drop of potassium hydroxide was allowed to fall into the solution until the end-point. The solution was stirred again. 10. Step 8 was repeated until the solution changed to a permanent pale purple colour. 11. All steps were then repeated for until a total of three readings within 0.1cm3 agreement were taken. 12. The readings were then recorded in a table and the concentration of the potassium hydroxide was calculated by taking two readings and calculating an average from them. ...read more.

Conclusion

/ 2 = 15.75 No mol in conical flask HC1 0.0025 No mol in average titre 1:1 = 0.0025 Further calculations n Concentration: 0.0025 / 15.75 = 0.00015873 15.75 / 1000 = 0.0157 c X v 0.0025 / 0.0157 = 0.15923 mol dm-3 Conclusion: Averages were taken of the readings so that a more accurate result was found. The aim of the experiment was to find the concentration of potassium hydroxide solution. Using the formula shown on the previous page the concentration was calculated to be 0.15923 mol dm-3. During the experiment a number of errors were observed as listed below: Errors: * When the funnel was removed, some drops of acid remained in the funnel. * When using the pipette to fill the burette, some drops of acid remained in the pipette. Should the experiment be repeated, these errors could be minimised by the following methods: * Average readings taken to repair errors caused by anomalous readings. * Empty both pipette and burette as much as is possible to minimise the errors. * Possibly repeat the experiment a total of 10 times in order to achieve a far more accurate result. ...read more.

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