Question

Turneric acid H₂T, is a diprotic acid with pKa₁ = 4.28 and pKa₂ = 9.67.

Which of these is the most abundant species at a pH of 3.78?

H₂T

HT^-    

T^2-

Which of these is the least abundant species at a pH of 3.78?

H₂T

HT^-

   T^2-

Which of these is the most abundant species at a pH of 4.78?

H₂T

HT^-

   T^2-

Which of these is the least abundant species at a pH of 4.78?

H₂T HT^-    T^2-

Which of these is the most abundant species at a pH of 9.17?

H₂T

HT^-

T^2-

Which of these is the least abundant species at a pH of 9.17?

H₂T

HT^-

    T^2-

Which of these is the most abundant species at a pH of 10.17?

H₂T

HT^-  

  T^2-

Which of these is the least abundant species at a pH of 10.17?

H₂T

HT^-  

  T^2-

Calculate the pH of a 0.077 M solution of H₂T. Report pH to ± 0.01.


Calculate the pH of a 0.077 M solution of NaHT. Report pH to ± 0.01.


Calculate the pH of a 0.077 M solution of Na₂T. Report pH to ± 0.01.

Answer 1

A pH above pKa of a proton, that proton will be deprotonated.

Turneric acid H2T, is a diprotic acid with pKa1 = 4.28 and pKa2 = 9.67.

1. at pH 3.78 it exists as H2T

2. T2- will be the least abundant species

3. HT- will be the most abundant species at pH 4.78

4.  HT- will be the most abundant species at pH 9.17

5. H2T will be the least abundant species at pH 9.17

6. T2- will be the least abundant species at pH 10.17

7. H2T will be the least abundant species at pH 10.17