On the plot, labels would be H2A HA- A^2- in the same order From the plot, junct
ID: 699588 • Letter: O
Question
On the plot,
labels would be H2A HA- A^2- in the same order
From the plot,
junction of H2A and HA-, pH = pKa1 = 5 ; Ka1 = 1 x 10^-5
From the junction of HA- and A^2-, pH = pKa2 = 9 ; Ka2 = 1 x 10^-9
pH = -log[H+] = 5.28
[H+] = 5.25 x 10^-6 M
fraction composition
[A] = [H+]^2 + Ka1[H+] + Ka1.Ka2 = (5.25 x 10^-6)^2 + 1 x 10^-5 x 5.25 x 10^-6 + 1 x 10^-5 x 1 x 10^-9
= 2.76 x 10^-11 + 5.25 x 10^-11 + 1 x 10^-14
= 8.01 x 10^-11
alpha[H2A] = [H+]^2/[A] = 2.76 x 10^-11/8.01 x 10^-11 = 0.344
alpha[HA-] = Ka1[H+]/[A] = 5.25 x 10^-11/8.01 x 10^-11 = 0.655
alpha[A^2-] = Ka1.Ka2/[A] = 1 x 10^-14/8.01 x 10^-11 = 1.25 x 10^-4
Explanation / Answer
Question 10 of 10 I eSapling Learning osition diagram of a diprotic acid (H2A) with pKa values of 5.00 and 9.00 H2A 1.00- 99e 0.90 2 0.80 2 0.70 0.60 Incorrect. At intermediate pH values, the intermediate form of the single proton, is the predominant form. 0.40 diprotic acid which has lost a 0.20 0.10 02 3 4 5 6 789 10 11 12 13 pH Calculate the fraction of the diprotic acid in each of its forms at phH 5.28 Number Scroil down Next