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The purpose of this experiment is to determine the concentration of a solution of sodium hydroxide by titration against a standard solution of potassium hydrogen phthalate.

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Introduction

Aim The purpose of this experiment is to determine the concentration of a solution of sodium hydroxide by titration against a standard solution of potassium hydrogen phthalate. Qualitative Data 1. Sodium hydroxide solution is colorless before titration 2. HCL is colorless before titration 3. The end result of the solution is slight pink 4. When the solution is off-shot the solution has a deep purple color 5. before reaching the endpoint the solution turns pink and then fades away as we swirl the conical flask 6. the color of phenolphthalein is colorless before titration 7. the color of phenolphthalein is slight pink after titration 8. a drop of the solution is left behind in the pipette 9. ideal color of the solution is fade pink Quantitative Data Table below shows the various volumes of chemicals that where used from their respected apparatus Apparatus / Chemicals used Reading taken from the apparatus Pipette solution (±0.06 cm3) 25 cm3 Burette solution (±0.02 cm3) 50 cm3 Phenolphthalein indicator 2 drops Standard C8H5O4K solution (±0.12 cm3) 250 cm3 Mean volume tittered 25.54cm3 Table below shows the number of trials taken from the NaOH solution from the burette and the intial and final values of the solution titrated No of Titration Trials (burette) Initial reading (±0.02ml) Final reading (±0.02ml) 1 0.09 ml 25.70 ml 2 0.1 ml 25.50 ml 3 0.09 ml 25.70 ml Table below shows the chemicals used and their concentration Apparatus / Chemicals used Concentration used Pipette solution (±0.06ml) ...read more.

Middle

The pipette completely drained the solution in the conical flask except only for a drop of solution to be left behind Evaluation 1. The NaOH solution was prepared by the lab technician of the concentration around 0.1M. The uncertainty in the error is unknown. This acts a drawback to our calculation and our experiment since we don?t know the amount of deviation the solution can have in its concentration. An improvement for this would be to use NaOH solution whose uncertainty is known so that we can calculate the error deviation in the final answer and hence be more precise and accurate in our calculation of the volume of NaOH solution titrated. 2. Distilled water used in preparing the sodium hydroxide solution was 99.9% pure. The impurities present in the distilled water could have added to the error calculation, hence increasing the deviation. In order to reduce the error inaccuracy distilled water with higher purity should be used. 3. An assumption is made that after the rinsing the burette and pipette with their respected solution there are no impurities left. This assumption could have added inaccuracies to the random error. Or another assumption that is the apparatus is clean and do not require rinsing could have also been made. Both of these assumptions stated above will lead to the reaction of the impurities with the respected solution hence consuming the moles and increasing the volume of the solution used to be titrated leading to an error in the calculation. ...read more.

Conclusion

Questions Q1.What effect would each of the errors described below have on the calculated value of the concentration of sodium hydroxide? 1. The burette is not rinsed with the sodium hydroxide solution 2. The pipette is not rinsed with the potassium hydrogen phthalate solution 3. The tip of the burette is not filled before titration begins 4. The conical flask contains some distilled water before the addition of potassium hydrogen phthalate. 1. If the burette is not rinsed with sodium hydroxide solution , there might be some impurities and when we add the sodium hydroxide solution , the molecules of the solution might react with the solution and hence will reduce the concentration of the solution 2. If the burette is not rinsed with the potassium hydrogen phthalate solution, there might be some impurities and when we add the potassium hydrogen phthalate solution , the molecules of the solution might react with the solution and hence will increase the concentration of the solution 3. If the tip of the burette is not filled , then a bubble remains in the tip of burette. This results in the solution taking a greater surface area in the burette and showing greater reading than the actual. So this will lead to decrease in the concentration because more volume will be used. 4. If the conical flask had some amount of distilled water before titration then more volume of the NaOH will be used to neutralize the acid , because the distilled water will dilute the acid, since more volume will be used the concentration of NaOH will reduce. ...read more.

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