Titration: Molarity of Acid or Base

Question

An aqueous solution of hydrochloric acid is standardized by titration with a 0.175 M solution of calcium hydroxide.

If 25.3 mL of base are required to neutralize 16.4 mL of the acid, what is the molarity of the hydrochloric acid solution?

________M hydrochloric acid

Answer 1

2HCl + Ca(OH)₂ ==> CaCl₂ + 2H₂O ... balanced equation

moles Ca(OH)₂ used = 25.3 ml x 1 L/1000 ml x 0.175 mol/L = 0.0044275 moles Ca(OH)₂

moles HCl present = 0.0044275 mol Ca(OH)₂ x 2 mol HCl/mol Ca(OH)₂ = 0.008855 moles HCl

Since there are16.4 ml HCl, and this is equal to 0.0164 L, we have...

Molarity of HCl = 0.008855 moles / 0.0164 L = 0.540 M (3 sig. figs.)