The mass of piece of sterling silver jewelry is 33.24 g. It contains 92.5% silver Ag by mass. Since, sterling silver is an alloy of Ag-Cu thus, percentage of Cu will be:
% Cu=100-92.5=7.5%
Thus, mass of copper will be:
[tex]m_{Cu}=\frac{7.5}{100}\times 33.24 g=2.493 g[/tex]
Molar mass of Cu is 63.546 g/mol, thus, number of moles of Cu can be calculated as follows:
[tex]n=\frac{m}{M}[/tex]
Here, m is mass and M is molar mass.
Putting the values,
[tex]n=\frac{2.493 g}{63.546 g/mol}=0.03923 mol[/tex]
Now, in 1 mole of Cu there are [tex]6.303\times 10^{23}atoms[/tex] thus, in 0.03923 mol, number of Cu atoms will be:
[tex]0.03923 mol\times 6.303\times 10^{23}atoms=2.363\times 10^{22} atoms[/tex]
Thus, number of atoms of Cu will be[tex]2.363\times 10^{22} atoms[/tex].
