How many moles are in 2.00 L of a 0.500 M Na2SO4 solution?

• A. 0.500 mol
• B. 1.00 mol
• C. 2.00 mol
• D. 0.250 mol

Answer: (B)

In a solution, molarity tells you how many moles are present per liter, so you find moles by multiplying the molarity by the volume in liters. The amount of Na2SO4 is 0.500 mol/L × 2.00 L = 1.00 mol. Since the question asks for moles of the dissolved compound itself, not the ions it forms, there’s no further multiplication. The three significant figures are preserved, so the result is 1.00 moles.