Question

How many grams of solute are in 1.00 liter of 0.200m na2so4 solution?

Answer 1

Molarity can be defined as the number of moles of solute in 1 L solution.
Molarity of Na₂SO₄ solution - 0.200 M
this means there are 0.200 moles in 1 L solution 
Molar mass of Na₂SO₄ - 142 g/mol 
therefore mass of Na₂SO₄ in 1.00 L - 0.200 mol x 142 g/mol = 28.4 g
a mass of 28.4 g of Na₂SO₄ is present in 1.00 L