A solution of barium hydroxide, #Ba(OH)_2# contains 4.285 grams of barium hydroxide in 100 mL of solution. What is the molarity of the solution?
We know the molar mass of barium hydroxide is 171.34 (you can google this or just add the mass of each atom in the molecule). Knowing that
This is done by dividing 4.285 g by the 171.34 g molar mass giving us 0.2500 mol of Ba(OH)2.
Plugging this all back into the equation for molarity we get