What is the molar concentration?

What was the molar concentration of the HCl solution? continued...?

• In order to determine the concentration of an HCl solution, a student titrated 10.00mL of the HCl solution with 0.1500M NaOH. After adding 26.18mL of the NaOH solution, the student realized he had inadvertently gone past the end point. The student then added 2.00mL more of the original HCl solution. The student then completed the titration requiring 1.65mL more of the NaOH solution. What was the molar concentration of the HCl solution?

• Answer:

  HCl(aq)+NaOH(aq)-->NaCl(aq)+H2O(l) No of moles of NaOH in 26.18mL of NaOH = [NaOH] x volume of NaOH in L = 0.15x26.18x10^-3 = 3.93x10^-3 No of moles of NaOH in 1.65mL of NaOH = [NaOH] x volume of NaOH in L = 0.15x1.65x10^-3 = 2.45x10^-4 No of moles of NaOH required = (3.93x10^-3)+(2.45x10^-4) = 4.18x10^-3 No of moles of HCl required= no of moles of NaOH required = 4.18x10^-3 [HCl]= no of moles of HCl required/volume of HCl required in L = (4.18x10^-3)/((10.00+2.00)x10^-3)) = 0.348M(answer) Note that [ ] denotes concentration and 1mL= 1000L. I hope this helps and feel free to send me an e-mail if you have any doubts!