("60.0 g Na"_2"SO"_4)/(1)*("1 mol Na"_2"SO"_4)/("142.04 g Na"_2"SO"_4) = "0.422 mol Na"_2"SO"_460.0 g Na2SO41โ
1 mol Na2SO4142.04 g Na2SO4=0.422 mol Na2SO4
The "142.04 g/mol"142.04 g/mol came from getting the molar mass of "Na"_2"SO"_4Na2SO4 from the Periodic table.
Multiply across the top (60 * 1=60)(60โ
1=60) and then divide by the bottom (1*142.04=142.04)(1โ
142.04=142.04) to get 0.4220.422 moles.