Question

How many milliliters of a .193 M HCl solution are needed to neutralize 221 mL of a 0.0351 M Ba(OH)₂ solution?

Answer 1

1 mol of Ba(OH)2 has 2 moles of OH- ion
number of moles of OH- = 2*M*V
                        = 2*0.0351*221
                        = 15.5142 mol

This should equal moles of H+

So,
moles of H+ = 15.5142 mol
M*V = 15.5142 mol
0.193*V = 15.5142 mol
V = 80.38 mL
AnsweR: 80.38 mL