Question

You have an unknown solution of HNO3 and a solution of 0.50 M KOH. You placed 20 mL of HNO3 into the flask and used 40 mL of KOH from the buret to complete the titration. Calculate the concentration of your unknown solution.

Answer 1

HNO3 is a strong acid, while KOH is a strong base. Both dissociate completely in water. Furthermore, they react with each other in a 1:1 ratio to produce KNO3 and H2O. This means if we know how many moles of KOH are present, the same number of moles of HNO3 must have been used to fully neutralize it.

moles of KOH = 0.5 M x 0.04 L = 0.02 mol

This means 0.02 mol of HNO3 were used as well. If it took 20 mL of HNO3 to neutralize the KOH, the HNO3 concentration was 0.02 mol/0.02 L = 1 M.