Ascorbic acid has two dissociation constants ka1 and ka2 Wha

Ascorbic acid has two dissociation constants, ka1 and ka2. What reactions do these constants refer to? Why is one of them so much larger than the other? Which one should you use to calculate the theoretical pH of a .5 M solution of ascorbic acid, and why?

Solution

reactions :

1) H2C6H6O6 <----------------------> HC6H6O6^-   + H+   , Ka1

2) HC6H6O6^-    <----------------------> C6H6O6^2-   + H⁺   , Ka2

Ka1 is much larger than Ka2 . the reason for this first ionisation is more than second ionisation

Ka1 is used to calculate theoretical pH due to almost all H+ ions comes from first ionization . the H+ ions comes from second ionization almost negligable