When barium hydroxide is titrated with hydrochloric acid, two molecules of hydrochloric acid combine with one molecule of barium hydroxide to produce one molecule of barium chloride and two molecules of water. The equation for this reaction is Ba(OH)2 + 2 HCl → BaCl2 + 2 H2O.
Ba(OH)2 is a strong base, while HCl is a strong acid. When the two are combined, they react with each other to form water and a simple salt. Like water, the simple salt has a neutral pH. Since barium chloride is fully soluble in water, the other notable observation when a strong base, such as Ba(OH)2, reacts with a strong acid, like HCl, is that an aqueous solution with a neutral pH is formed.