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Determination of the proportion of nitrogen in a fertiliser.

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Introduction

Name: Tan Choon Liang Title: Determination of the proportion of nitrogen in a fertiliser Date: 04.10.2004 Class: Year 13 Chemistry Higher Level Teacher's Dr.Dickinson name: Choon 04.10.2004 Determination of the proportion of nitrogen in a fertilizer Results: Additional details for method: When boiling the mixture until no more ammonia is evolved, an indicator was needed to identify the point at which no more ammonia was being created. The indicator used was damp blue litmus paper and in the presence of ammonia, it would turn red. This was used sporadically to check whether ammonia was still being released. Only when no more ammonia was being evolved could the experiment be carried on. For the titration, the suitable indicator being used was methyl orange. The different levels of color changes is the main indication. When the solution with the indicator is yellow, it means that it's still alkaline, when it turns orange, it means that the solution has turned neutral and when it turns to pink, it means that the solution is then acidic. This is a good indicator to tell when too much acid has been used. When too much acid is used, it turns pink and therefore, the color which is to be obtained is orange, in order to accurately measure on which exact point does the solution become neutral. Raw Data: Weight of empty weighing bottle: (g) 13.888 Weight of bottle + fertilizer: (g) ...read more.

Middle

0.02653 x 14.01 = 0.3716853 grams To figure out the exact proportion between the amount of nitrogen and the total amount of fertilizer, the percentage needs to be calculated: 0.3716853 x 100 = 24.01067829 % 1.548 Therefore, the percentage of nitrogen in the fertilizer = 24.01 % From this, the overall uncertainty can then be calculated = 0.6210690429 x 24.01 % = 0.1491228899 100 = 0.15 Therefore, Overall uncertainty = 24.01% � 0.15% Conclusion: From the results obtained, it can be seen that there is approximately 24.01% of nitrogen found in the fertilizer we used. This means that in all the different kinds of salts in this fertilizer, 24.01% of it had nitrogen in it. There are not exactly accurate literature values because in this experiment we didn't know what kind of fertilizer we were dealing with. The exact compound formula wasn't given and there so many different types of fertilizers. Therefore, no comparison with literature values can be obtained. However, from one of literature values, there is one type of fertilizer that comes close to this value. Ammonium sulfate carries 20.5% of nitrogen, and that is fairly close to this result obtained from this experiment. Therefore, it can only be predicted that the type of fertilizer being used in this experiment was ammonium sulfate. The multiple number of steps needed to be conducted in this experiment causes an increase in the chances of errors which could affect the final result. ...read more.

Conclusion

o The many steps in this titration, the multiple occurrences of having to use the pipette is a large factor because by having more steps to conduct, it'll create more chances of both human and manipulation errors. Accidental spills or contaminations from the long list of instruments that had to be used could occur multiple times throughout this whole experiment. Any of it could easily affect the results of the experiment by quite a lot. Thus, all this is shown by the uncertainties calculations. o In each of the attempts, the quickness and speed of moving the conical flask around would be different in each case. The conical flask was being moved around to mix the solutions properly as an act of trying to stir the solutions. However, this caused more errors because it meant that in each attempt, the only correct way was to shake it around at a constant speed in all trials, but that is impossible for anyone to regulate with their arms. Each attempt would have its own speed in strength of shaking. o Parallax error of not recording down the exact measurement could've occurred. Although attempts to minimize the error, by using a white surface behind the burette to see it clearly, there is always room for some minor errors in reading it wrongly. o When observing and reacting to when the yellow color of the methyl orange in alkaline solution, would change to orange in the presence of a neutral solution, it is difficult because the different shadings is extremely hard to differentiate when one looks at the solution for a long period of time. ...read more.

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