25.00cm3 of 0.100m NaOH is needed to titrate 25.00cm3 of a solution of hydrochloric acid, calculate the concentration of the acid

The balanced chemical reaction is:

HCl + NaOH - > NaCl + H2O

We see that there is a 1:1 mole correspondence

First calculate the moles of NaOH:

moles NaOH = 0.100 M * 0.025 L = 0.0025 mol

Therefore the molarity of HCl is:

Molarity HCl = 0.0025 mol / 0.025 L = 0.100 M