Question

Ba(OH)2(aq) + HCl(aq) BaCl2(aq) + H2O (g)
Consider the unbalanced equation above. What is the concentration of the original hydrochloric acid solution if 18.0 mL of the acid reacts with 45.5 mL of 0.280 M barium hydroxide?

Answer 1

Ba(OH)2(aq) + 2HCl(aq) BaCl2(aq) + 2H2O (g)

molBa(OH)2 = M x L = ?
Now using the coefficients in the balanced equation, convert mols Ba(OH)2 to mols HCl.
Finally, M HCl = mols HCl/L HCl.