what volume of a 0.247 M perchloric acid solution is required to neutralize 23.8 mL of a 0.156 M calcium hydroxide solution?
_titration problem of acids/bases
2HClO4 + Ca(OH)2 ==> 2H2O + Ca(ClO4)2
mols Ca(OH)2 = M x L = ?
mols HClO4 = 2x that.
M HClO4 = mols HClO4/L HClO4. You have mols and M, solve for L.