Question

For a diprotic acid, pKa2 is _____ pKa1. (Choose the best answer.)

a. less than
b. unrelated to
c. equal to
d. greater than

Answer 1

For a diprotic acid, pKa2 is greater than pKa1, indicating that the removal of the first proton happens more easily than the second.

Step-by-step explanation:

For a diprotic acid, pKa2 is greater than pKa1. This is due to the fact that each successive ionization reaction is less extensive than the former for polyprotic acids, including diprotic acids. The first ionization constant is larger because the fully protonated molecule tends to lose a proton more easily than the once-deprotonated form. The difference between successive ionization constants of a diprotic acid typically differs by a factor of about 105 to 106, indicating that the first proton is removed much more readily than the second.