To find the concentration of hydrochloric acid HCl in the solution, we can use the concept of stoichiometry and the balanced chemical equation for the neutralization reaction between HCl and NaOH:HCl + NaOH NaCl + H2OFrom the balanced equation, we can see that 1 mole of HCl reacts with 1 mole of NaOH.We are given that 50 mL of 0.1 M NaOH is required to neutralize the HCl solution. First, we need to find the moles of NaOH used in the reaction:moles of NaOH = volume L concentration M moles of NaOH = 0.050 L 0.1 M = 0.005 molesSince the mole ratio of HCl to NaOH is 1:1, the moles of HCl in the 100 mL solution will also be 0.005 moles.Now, we can find the concentration of HCl in the 100 mL solution:concentration M = moles of HCl / volume L concentration M = 0.005 moles / 0.100 L = 0.05 MSo, the concentration of hydrochloric acid HCl in the 100 mL solution is 0.05 M.