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Determination of the relative atomic mass of Lithium using Titration.

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Introduction

Experiment (Titration) Determination of the relative atomic mass of Lithium Aim: To determine the relative atomic mass of Lithium Introduction: In this investigation I will determine the relative atomic mass of Lithium by two different methods. * First I will measure the volume of Hydrogen gas * Secondly by titrating the Lithium Hydroxide produced Apparatus * Safety Spectacle * Filter funnel * Burette, 50 cm3 * Clamp stand * Pipette one 25cm3 * Teat pipette * 2 Conical flask 25 cm3 * Beakers * 25cm3 Measuring Cylinder * Phenolphthalein indicator solution * Hydrochloric acid solution * Stopper * Wash bottle of distilled water Method 1 1. Set up the equipments as stated below. 2. Measure the exact 100.0cm3 of distilled water and add into 250cm3 conical flask. 3. Weigh about 0.10g of lithium. Record the exact mass of lithium using an appropriate format. 4. Remove the stopper, add the lithium to 100cm3 of distilled water in conical flask, and quickly replace the stopper. ...read more.

Middle

2. Using pipette 25.0 cm3 of the solution in the conical flask from method 1 into a clean 250 cm3 conical flask and add 5 drops of Phenolphthalein indicator. 3. Titrate with 0.100mol dm3 Hydrochloric acid. 4. Record the results in an appropriate format. 5. Repeat the titration to obtain consistence results. Show all of the results. 6. Record the average titre. Diagram for method 2 Hydrochloric acid Lithium hydroxide and Phenolphthalein indicator Results Table Trial 1 2 Burette Final 44.5 42 41.5 Initial 0 0 0 Volume used (titration) / cm3 44.5 42 41.5 Mean titration /cm3 44.5 + 42 + 41.5 = 128/3 = 42.7 Calculation LiOH(aq) + HCl(aq) LiCl(aq) + H2O(l) 1. Moles of HCl used in titration Moles = molarity x volume = 0.100 x (42.7/1000) = 0.00427 2. No. of moles of LiOH = 0.00427 as the ratio is 1:1. 3. No. of moles of LiOH present in 100cm 3 of the solution from method 1 = 25 /100 = 4 Therefore 0.00427 x 4 = 0.01708 4. ...read more.

Conclusion

I had to take three readings to get the sufficient mean titration result, which required a lot of time to do this. Accuracy By taking results for three times allowed me to gain a good average of the concentration. Also the use of three results meant that the reliability and the accuracy of my results were high. Problems encountered The main problem was that it was difficult to put the measuring cylinder full of water into the plastic box of water up side down to collect gas. The second problem was that I did not rinse the conical flask every time after each titration therefore more titration was required. And the titre readings were not similar. Improvements By looking at the above problems I would use the gas syringe to measure the hydrogen gas. I would rinse the flask out properly to ensure that it is fully cleansed and ready for the next part of the investigation. Extension As an extension to the investigation I could use other elements, to calculate the their relative atomic mass and compare them. ...read more.

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