A chemistry student wants to find the concentration of a hydrochloric acid (HCl) solution. To do this, the student performs a titration experiment with a sodium hydroxide (NaOH) solution of known concentration. The student adds 25 mL of the HCl solution to a flask with an indicator, and then slowly adds the NaOH solution until the indicator changes color. It was found that it took 18.2 mL of the 0.1 M NaOH solution to reach the endpoint. What is the concentration of the HCl solution?

Question

A chemistry student wants to find the concentration of a hydrochloric acid (HCl) solution. To do this, the student performs a titration experiment with a sodium hydroxide (NaOH) solution of known concentration. The student adds 25 mL of the HCl solution to a flask with an indicator, and

Answer 1

To find the concentration of the HCl solution, we can use the concept of moles and the balanced chemical equation for the reaction between HCl and NaOH:HCl  aq  + NaOH  aq   NaCl  aq  + H2O  l From the balanced equation, we can see that 1 mole of HCl reacts with 1 mole of NaOH.First, we need to find the moles of NaOH used in the titration:moles of NaOH = volume of NaOH  L   concentration of NaOH  M moles of NaOH = 18.2 mL   1 L / 1000 mL   0.1 Mmoles of NaOH = 0.0182 L  0.1 Mmoles of NaOH = 0.00182 molesSince the mole ratio of HCl to NaOH is 1:1, the moles of HCl in the 25 mL solution are equal to the moles of NaOH:moles of HCl = 0.00182 molesNow we can find the concentration of the HCl solution:concentration of HCl = moles of HCl / volume of HCl  L concentration of HCl = 0.00182 moles /  25 mL  1 L / 1000 mL concentration of HCl = 0.00182 moles / 0.025 Lconcentration of HCl = 0.0728 MThe concentration of the HCl solution is approximately 0.0728 M.