To find the concentration of the hydrochloric acid HCl solution, we can use the concept of stoichiometry and the balanced chemical equation for the 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 concentration M moles of NaOH = 0.025 L 0.100 Mmoles of NaOH = 0.0025 molesSince the mole ratio between NaOH and HCl is 1:1, the moles of HCl in the reaction are also 0.0025 moles.Now, we can find the concentration of the HCl solution using the formula:concentration M = moles of HCl / volume of HCl solution L First, convert the volume of HCl solution from mL to L:30.0 mL = 0.030 LNow, find the concentration of HCl:concentration M = 0.0025 moles / 0.030 Lconcentration M = 0.0833 MTherefore, the concentration of the hydrochloric acid HCl solution is 0.0833 M.