In a titration of 0.5 M HCl and an unknown concentration NaOH, 25.0 ml of NaOH was required to completely neutralize 25.0 ml of HCl. What is the concentration of the NaOH?

When an acid is neutralized by a base, that means moles of H + = moles of OH-

moles of H + = 0.5 M * 0.025 L HCl = 0.0125 moles H+

moles of OH - should be equal to 0.0125 moles, so

0.0125 moles = (x) * 0.025 L NaOH

x is the concentration of NaOH, which we want to find.

x = 0.5 M

The correct answer is C) 0.5 M.