Answer:
0.60 moles of Na₂SO₄
Step-by-step explanation:
Molarity is an unit of concentration defined as the ratio between moles of solute and liters of solution.
A solution of Na₂SO₄ 0.40M contains 0.40 moles of solute (Na₂SO₄) per liter of solution.
As you have 1.5L of solution, moles of Na₂SO₄:
1.5L × (0.40mol / L) = 0.60 moles of Na₂SO₄