Determination of Relative atomic mass of lithium

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 Assessed Practical 3

Determination of Relative atomic mass of lithium

Jared Ching

Evaluation:

        In general the accuracy of the experiments was good. However with practice, the accuracy could be improved; accuracy being how close the results are to the real answer. I think I have carried pit the experiment as well as I possibly could at the time with the given conditions and time period allowed. I have gained precise results from the practical. However, looking back at the analysis section, the relative atomic mass values I found were not exactly 6.9 as presented in the periodic timetable. Method (1) gave me 8.28; a difference of 1.38 and method (2) gave me 7.37, a difference of 0.43 to the real/reference value. Therefore method (2) proved to be more accurate. Overall the results were good and came close to the real values. There were no anomalous results.

        

Limitations:

The main sources of error that I found to be evident and which were out of my control were as follows:

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  • In method (1), due to the oil that lithium is stored in, not only caused problems with weighing it, but also when I attempted to quickly put pieces of lithium into the chonical flask with distilled water, some pieces “stuck” on the weighing boat, sue to residue oil having a “sticky” effect. This caused a delay in the whole process and I was not able to place the bung in place immediately, thus hydrogen was lost making the gas collected less than what it was supposed to be.
  • When weighing lithium the percentage error was:

(0.00005/0.00645) x 100= ...

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