Question

A solution is made by dissolving 15.1 g of barium hydroxide, Ba(OH)₂, in enough water to make exactly 100. mL of solution. Calculate the molarity of each species:

Ba(OH)₂ _______ mol/L

Ba²⁺ _________ mol/L

OH^- _________ mol/L

Answer 1

Barium hydroxide is consider to be a strong base so it dissolves completely. One molecule of barium hydroxide dissociate in the water to produce three ions as follows,

Ba(OH)₂ (aq) --> Ba²⁺_(aq) + 2OH^-_(aq)

Now, molar mass of barium hydroxide= 171.34 g/mol

15.1 g of barium hydroxide means 15.1/171.34 = 0.08812 moles of barium hydroxide

0.08812 moles of barium hydroxide dissolved in 100ml of solution , therefore molarity of solution = 0.08812/0.1L = 0.8812M

As per above equation molarity of Ba²⁺ = 0.8812 mol/L

Molarity of OH^- = 2*0.8812 = 1.762 mol/L