# Determining the Relative Atomic Mass of Lithium.

Nathan Stokes                Lithium Coursework

Determining the Relative Atomic Mass of Lithium.

To calculate the relative atomic mass, the moles of H2 produced when Li reacts with HCl.

On the first attempt 181cm3 of H2 was collected. The molarity of H2 must be found to enable us to calculate the relative atomic mass of lithium.

1 mole of gas occupies 24dm3 at room temperature and pressure.

1/24000 x 181 = 0.0075 Moles of H2

2Li(s)  +  2H2O(l)    2LiOH(aq)  +  H2(g)

The moles of Li that reacted must now be found.

This result must multiply this result by 2 as Hydrogen as a gas is a diatomic particle (there are 2 atoms of hydrogen).

=  2  x  0.0075 M

=  0.0150M          Therefore in 1g of Lithium reacts with H2O there is 0.015M moles of hydrogen given off.

Relative Atomic Mass = Mass / Molarity

Relative Atomic Mass = 0.1 / 0.015  = 6.66

The second attempt 174cm3 of H2 was collected.

1/24000  x  174 = 0.00731 M

2 x 0.00731 =  0.0146 M

Ar = 0.1 / 0.0146 = 6.9

173cm3 of H2 was collected during the final attempt.

1/24000  x  178 = 0.00748 M

2 x  0.00748  =  0.01496 M

Ar = 0.1 / 0.01496  =  6.7

Average Relative atomic Mass = 6.66 +  6.9  +  6.7 = 6.75

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Titration Calculations.

The titration was ...