Hydrochloric acid and barium hydroxide react to form barium chloride and water. It is a process of neutralization because an acid reacts with base to form salt and water. HCl is an acid and Ba(OH)2 is a base.
HCl ------> H+1 + Cl-1
Ba(OH)2 ------> Ba+2 + 2OH-1
The balanced ionic equation for the reaction is;
2 HCl(aq) + Ba(OH)2(aq)====> BaCl2(aq) + 2 H2O(l)
Two molecules of hydrochloric acid react with one molecule of barium hydroxide to form one molecule of barium chloride and two molecules of water.