In order to determine the concentration of a solution of Carbonic Acid (H2CO3), a sample was placed in a buret and titrated with 0.1132 M Sodium hydroxide. For the carbonic acid, the initial reading was 11.0ml and final reading was 31.0 ml. For sodium Hydroxide, the initial reading was 1.2 and the final reading was 46.4ml. What is the concentration of the carbonic acid?

Answer 1

H2CO3 + 2NaOH ==> Na2CO3 + 2H2O OR
H2CO3 + NaOH ==> NaHCO3 + H2O

This problem is not workable with the information given. The titration of H2CO3 has TWO endpoints as shown in the two equations above. If phenolphthalein is used as the indicator the second equation is in effect. If methyl red indicator is used it's the first equation.