To solve this problem, we can use the concept of stoichiometry and the balanced chemical equation for the reaction between hydrochloric acid HCl and sodium hydroxide NaOH :HCl aq + NaOH aq NaCl aq + H2O l From the balanced equation, we can see that the mole ratio of HCl to NaOH is 1:1.First, we need to find the moles of NaOH used in the reaction:moles of NaOH = volume of NaOH L concentration of NaOH M moles of NaOH = 0.030 L 0.1 Mmoles of NaOH = 0.003 molesSince the mole ratio of HCl to NaOH is 1:1, the moles of HCl in the reaction are also 0.003 moles.Now, we can find the concentration of the HCl solution:concentration of HCl M = moles of HCl / volume of HCl L concentration of HCl M = 0.003 moles / 0.025 Lconcentration of HCl M = 0.12 MTherefore, the concentration of the hydrochloric acid solution is 0.12 M.