This has multiple answers can you be more specific
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
A chemical change affects on the molecular level of matter, which makes it irreversible. Combustion is a pretty good exmple. Physical changes are reversible and dont alter the formula. Hope this helped!