In a titration between sodium hydroxide (NaOH) and hydrochloric acid (HCl), the balanced chemical equation is as follows:
NaOH + HCl -> NaCl + H2O
From the balanced equation, we can see that one mole of NaOH reacts with one mole of HCl to produce one mole of NaCl and one mole of water.
Given that the concentration of NaOH is 0.1 M, we can use the stoichiometry of the balanced equation to determine the concentration of HCl used in the titration.
Since the mole ratio between NaOH and HCl is 1:1, the concentration of HCl will also be 0.1 M. This is because the concentration of the acid being titrated is the same as the concentration of the base being used.
Therefore, both the NaOH and HCl solutions in the titration have a concentration of 0.1 M.