Question

Calculate the mass of one atom of silver given atomic mass of silver is 108 g.

Answer 1

The atomic mass of silver is 108 u and molar mass of silver is 108 g/mol. This means there are $6.023\times {10}^{23}$ atoms of silver in 108 of silver. Thus
$6.023\times {10}^{23}$ atoms of silver =108g
1 atom of silver = $\frac{108}{\left(6.023{\times }^{23}\right)g}$
$=1.7931\times {10}^{-22}g$
Thus the mass of an atom of silver is $1.7931\times {10}^{-22}g.$
The atomic mass of carbon is 12 u while that of oxygen is 16 u. The chemical formula of carbon dioxide is $C{O}_2$, so the molecular mass of carbon dioxide is $12+2\times \left(16\right)=44u.$ The molar mass of carbon dioxide is 44g. This means there are $6.023\times {10}^{23}$ moleucles of $C{O}_2$ in 44 g of $C{O}_2$. Thus
$6.023\times {10}^{23}$ moleucles of $C{O}_2=44g$ of $C{O}_2$
1 molecule of $C{O}_2=\frac{44}{(6.023\times {10}^{23})g}$
$=7.305\times {10}^{-22}g$
So the mass of a moleucle of $C{O}_2=7.305\times {10}^{-22}g$
A mole is a convenient counting unit whenever one is dealing with numbers of atoms or molecules. It is equal to Avogadro's number (NA), namely $6.022\times {10}^{23}$. If we have one mole of water, then we know that it will have a mass of 2 grams (for 2 moles of H atoms) +16 grams (for one mole O atom) =18 grams.