exactly 25.0 mL of an aqueous solution of barium hydroxide required 32.0 mL of 0.200 M nitric acid to neutralize it. what is the concentration of the barium hydroxide solution?

Answer 1

Always write the correctly balanced equation before doing these problems:

Ba(OH)₂(aq) + 2HNO₃(aq) ==> 2H₂O(l) + Ba(NO₃)₂(aq) ... balanced equation

note the stoichiometry ... 2 mols HNO₃ for each 1 mol Ba(OH)₂

Now we can use dimensional analysis and the noted stoichiometry to solve the problem:

32.0 ml HNO₃ x 1 L/1000 ml x 0.200 mol / L = 0.0064 mols HNO₃ used

0.0064 mol HNO₃ x 1 mol Ba(OH)₂ / 2 mols HNO₃ = 0.0032 mol Ba(OH)₂ present

Concentration of Ba(OH)₂ = mols/L = 0.0032 mols / 0.0250 L = 0.128 M