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# mass of magnesium

Extracts from this document...

Introduction

DETERMINATION OF RAM OF MAGNESIUM Method1 Mass of Mg = 0.12g Volume of Hydrogen = 128cm3 Treatment of results Mg + 2HCl ==> MgCl2 +H2 * n= v?V ==> 128 ?24000 = 5.33?10-( moles * mole ratio is 1:1, therefore moles of mg that reacted= 5.33?10-( moles * RAM of Mg (n= m?M ==> M= m?n) ==> 0.12 ? 5.33?10-( = 22.51 Method2 Mass of magnesium from method 1 = 0.12 Weight of boat = 44.17 Weight of boat with solution = 52.84 Weight of boat with salt (MgCl2) = 44.74 o Mass of MgCl2 formed = 44.74 ? 44.17 = 0.57 o Mass of Cl- ions = 0.57 ? 0.12 = 0.45g o n= m ?M = 0.45 ? 35.5 = 0.013moles o n= m ?M = 0.57 ? 24.3 = 0.023moles EVALUATION Method Result 1 22.5 2 18.9 Expected 24.3 From looking at the end results in both methods, I can clearly see that method 1 was the more accurate and appropriate way to determine the mass of magnesium. This is because out of both results, method 1 had the closer answer to the expected than method 2. Method1 only had a difference of 1.8 from the actual RAM of magnesium, whereas Method2 had a difference of 5.4- which is quiet a large difference. ...read more.

Middle

Loss of H2 before placing bung This lowers the volume of hydrogen gas measured that was produced from experiment. Lowered the RAM of magnesium at the end because it lowered the moles of H2 that we collected therefore lowering the moles of Mg that reacted. Both methods were only carried out once The results that we got could have been anomalous results. If the results were anomalous, this could have explained why the RAM in method2 was so far from the expected. Improvements: to minimise the procedural errors, we could have repeated the experiments in both methods at least 3-4 times because in this case we would have been able to recognize the anomalous results and worked on the more accurate results. Because in method2, the reason for getting 22% experiment error could have been due to human error and we did not realize because we only carried out the experiment once. Also this makes the results for both methods unreliable. Another possibility would have been to use a magnesium strip that was not coated with any impurities, this is because even though we spent time cleaning the strip, there were still some impurities left on it that we could not take off, therefore it was not pure magnesium and some weight was added to it therefore increasing the RAM at the end. ...read more.

Conclusion

If we had used a 3.d.p balance at the beginning of method1, we would have had more significant because 3.d.p is a higher degree of accuracy than 2.d.p. Also the measuring cylinder although its error was insignificant, but because we had to read it upside down, this increased the chances of us making an incorrect reading; therefore having an error carried forward. Overall, according to the measurement errors, method 2 seems like a more significant and accurate procedure to follow in order to determine the RAM of an element. I think this because it uses less apparatus with low measurement errors which reduces the total measurement error for the method; therefore it gives a more reliable result having a small effect on the final result. The reason to why when I did the experiments method1 seemed more accurate was possibly because of the errors carried forward to method 2 on top of its own errors. RELIABILITY: I feel that my results were not reliable because reliability is repeatability - and I did not repeat any of my methods. If I had repeated my experiments at least 3 times, I would have been able to recognize any anomalous results and therefore would have gained more accurate and reliable results for the RAM of Mg. ?? ?? ?? ?? Fatima Omar Determination of RAM of Mg 1 ...read more.

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