# How many moles of sodium carbonate are present in 6.80 grams of sodium carbonate?

There are $\text{0.0642 mol Na"_2"CO"_3}$ in $\text{6.80 g}$.
The chemical formula of sodium carbonate is $\text{Na"_2"CO"_3}$. The molar mass of sodium carbonate is $\text{105.988439 g/mol}$. http://pubchem.ncbi.nlm.nih.gov/compound/sodium_carbonate
6.80cancel("g Na"_2"CO"_3)xx(1"mol Na"_2"CO"_3)/(105.988439cancel("g Na"_2"CO"_3))="0.0642 mol Na"_2"CO"_3"