Chem3-molar Mass Of Lithium 2dl44

Name : Nikman Adli b. Nor Hashim (M04D) Title : Determination of the Relative Atomic Mass of Lithium. Data collection : Quantitative data : Method 1: Mass of Lithium used : 0.0120 + 0.0001 g. Volume of the distilled water used : 100.0 cm³. Volume of hydrogen gas evolved : 16.10 cm³. Method 2: Table 2.0 : Volume of Hydrochloric Acid in the experiment.

Initial burette reading (cm³) + 0.05cm³ Final burette reading (cm³) + 0.05cm³ Volume of HCl used (cm³) + 0.1cm³

1

2

3

0.00

0.00

0.00

39.40

36.00

35.30

39.4

36.0

35.3

Volume of Lithium Hydroxide used : 25.0 cm³. Molarity of Hydrochloric Acid used : 0.01 moldm-3. Qualitative data : The colour indicator (phenolphthalein) in the LiOH solution changes from pink to colourless. The hydrochloric acid used to counterbalance the LiOH solution did not change a lot from its theoretical volume.So, that means that the end point of the titration has been reached.

Data processing : Method 1 : The chemical equation : 2Li + 2H2O  2LiOH + H2. The volume of hydrogen gas evolved : 16.10 cm³. The number of moles of H2 : = Volume of H2 gas (dm³) STP or Room Temperature = 16.10cm³ 1000(24) = 0.00067 mol. 2 mol of Lithium  1 mol of Hydrogen gas 0.00134 mol of Lithium  0.00067 mol of Hydrogen gas The molar mass of Lithium : Molar mass = mass(g) moles Mb

= 0.0120 g 0.00134 = 8.955g/mol.

Method 2 : The chemical equation : LiOH + HCl  LiCl + H2O. The volume of hydrochloric acid used : = ( 39.4 + 36.0 + 35.3 )cm³ 3 = 36.9 cm³. The molarity of hydrochloric acid used = 0.01 mol/dm³. MaVa = MbVb Mb = MaVa Vb = (0.01 mol/dm³)(36.9cm³) 25.0cm³ = 0.01476 mol/dm³. Number of mole of Lithium Hydroxide : MV = (0.01476mol/dm³) (100cm³) 1000 1000 = 0.001476 mol. 2 mol of LiOH  2 mol of Li 0.001476 mol of LiOH  0.001476 mol of Li The molar mass of Lithium : Molar mass = mass(g) moles Mb

= 0.0120 g 0.001476 = 8.130 g/mol.

Everage molar mass of Lithium : Molar mass in method 1 + Molar mass in method 2 2 8.955 g/mol + 8.130 g/mol 2 = 8.543 g/mol. Error analysis : The actual molar mass of Lithium = 6.94 g/mol. The percentage of differences = |6.940 - 8.543| x 100 6.94 = 23.100 %.

Suggestion and limitations : 1) All readings are not constant. 2) LiOH in the conical flask was not well shaked. 3) Try to make more reading during titration (4 to 5 readings). 4) The mass of Lithium must be take higher value to get a better average of hydrogen gas evolved.

Conclusion : From the experiments, the molar mass of Lithium that I got is 8.543 g/mol.From calculation, the percentage error of my experiment is 23.100%.