Week 10 Question 2

When doing a titration of a polyprotic acid, one starts with a solution of the polyprotic acid in a flask and incrementally adds titrant (strong base such as NaOH) to the solution. The pH can be calculated at various points in the titration, starting with zero added titrant. Some very useful points are the half-equivalence point, the first equivalence point, half way to the second equivalence point and the second equivalence point. 

Using the system of 25.0 mL of 0.050 M malonic acid, H₂C₃H₂O₄ titrated with 0.025 M NaOH, calculate the pH at the following points: 

    First person: zero added NaOH (initial point in the titration)

    Second person: first half equivalence point

    Third person:   first equivalence point

    Fourth person: second half equivalence point

    Fifth person:  second equivalence point

    Sixth person: after adding 150 mL of the NaOH

If we finish with this, I will put up a second system.