Question

A 250-ml sample of na2so4 is reacted with an excess of bacl2. if 5.28 g baso4 is precipitated, what is the molarity of the na2so4 solution?

Answer 1

To get the molarity you need to follow this equation
moles of solute
Molarity (M = -----------------------
Liters of solution

But before you apply that equation you need to find the moles of solute and the liters of solution. Follow this equation

Na2SO4 + BaCl2 = BaSO4 + 2 NaCl

Solution

Moles of BaSO4 = 5.28 g
---------------
233.43 g / mol
= 0.0226 moles
Moles of NaSO4 = 0.0226
0.0226 mole
Molarity = -----------------
0.250 L
= 0.0905 mol / L

So the answer is 0.0905 mol / L