Calculate the number of aluminium ions present in 0.051 g of aluminium oxide (Al2O3). (Atomic masses: Al = 27 u; O = 16 u)
Molecular mass of aluminium oxide (Al2O3)
= 2×27+3×16
=54+48
= 102
Number of moles of aluminium oxide
=Given mass/Molar mass
=0.051/102
=0.0005 mol
As 1 mole of aluminium oxide contains 2 moles of aluminium.
So, 0.0005 mole of aluminium oxide contains = 0.0005 ⅹ 2
0.0005 mole of aluminium oxide contains = 0.001 mole of Aluminium
As 1 mole contains 6.022 ⅹ 1023 ions
Therefore, 0.001 moles of aluminium oxide,
= 6.022 ⅹ 1023 ⅹ 0.001 ions
= 6.022 ⅹ 1020 ions of aluminium
Hence, 0.051 g of aluminium oxide contains 6.022 ⅹ 1020 ions of aluminium.
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