To find the concentration of the hydrochloric acid solution, we can use the concept of stoichiometry and the balanced chemical equation for the neutralization reaction between sodium hydroxide NaOH and hydrochloric acid HCl :NaOH + HCl NaCl + H2OFrom the balanced equation, we can see that the mole ratio between NaOH and HCl is 1:1.First, we need to find the moles of NaOH used in the reaction:moles of NaOH = volume L molaritymoles of NaOH = 0.025 L 0.1 M = 0.0025 molesSince the mole ratio between NaOH and HCl is 1:1, the moles of HCl are also 0.0025 moles.Now, we can find the concentration of the HCl solution:molarity M = moles of HCl / volume of HCl solution L molarity M = 0.0025 moles / 0.020 L = 0.125 MSo, the concentration of the hydrochloric acid solution is 0.125 M.