Question

Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)
A. `6.023xx10^20` ions
B. 3 ions
C. `6.023xx10^23` ions
D. 9 ions

Answer 1

Mass of `Al_2O_3 = 2xx27+3xx16=102`
0.051g of `Al_2O_3 = (0.051)/(102)=0.0005` mol
1 mol of `Al_2O_3 " contains " 2xx6.023xx10^23 Al^(3+)` ions
0.0005 mol of `Al_2O_3 " contains " 2xx0.0005xx6.023xx10^23`
`Al^(3+) " ions " = 6.023xx10^20 Al^(3+)` ions