Question

If 20.0 mL of Ca(OH)2 with an unknown concentration is neutralized by 37.5 mL of 0.124 M HCl, what is the concentration of the Ca(OH)2 solution? Show all of the work needed to solve this problem.
Ca(OH)2 + 2 HCl 2 H2 O + CaCl2

Answer 1

The balanced chemical reaction is:

Ca(OH)2 + 2 HCl = 2 H2 O + CaCl2

We are given the amount of hydrochloric acid to be used in the reaction. This will be the starting point for the calculations.

0.124 mol HCl / L soln ( .0375 L solution) ( 1 mol Ca(OH)2 / 2 mol HCl) / 0.020 L Ca(OH)2 solution = 0.12 mol / L Ca(OH)2 = 0.12 M