To find the concentration of the hydrochloric acid solution, we can use the concept of titration and the equation:moles of acid = moles of baseWe are given the volume and concentration of the sodium hydroxide solution, so we can find the moles of sodium hydroxide using the equation:moles = volume L concentration M moles of NaOH = 15 mL 0.1 MFirst, convert the volume from mL to L:15 mL = 0.015 Lmoles of NaOH = 0.015 L 0.1 Mmoles of NaOH = 0.0015 molesSince the moles of acid and base are equal in a neutralization reaction, we have:moles of HCl = moles of NaOHmoles of HCl = 0.0015 molesNow we can find the concentration of the hydrochloric acid solution using the equation:concentration M = moles / volume L We are given the volume of the hydrochloric acid solution 25 mL , so we can convert it to liters:25 mL = 0.025 LNow we can find the concentration of the HCl solution:concentration of HCl = 0.0015 moles / 0.025 Lconcentration of HCl = 0.06 MSo, the concentration of the hydrochloric acid solution is 0.06 M.