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 HCl and sodium hydroxide NaOH :HCl + NaOH NaCl + HOFrom the balanced equation, we can see that one mole of HCl reacts with one mole of NaOH. We can use the volume and concentration of NaOH to find the moles of NaOH, and then use the stoichiometry to find the moles of HCl. Finally, we can use the volume of HCl to find its concentration.1. Calculate the moles of NaOH:moles of NaOH = volume L concentration M moles of NaOH = 0.018 L 0.1 Mmoles of NaOH = 0.0018 moles2. Use stoichiometry to find moles of HCl:moles of HCl = moles of NaOH since the mole ratio is 1:1 moles of HCl = 0.0018 moles3. Calculate the concentration of HCl:concentration M = moles of HCl / volume L concentration M = 0.0018 moles / 0.025 Lconcentration M = 0.072 MSo, the concentration of the hydrochloric acid solution is 0.072 M.