Chapter 14 Extra Credit Problem 14.21 5 of 10 Part A Like sulfuric acid, selenic

Question

Chapter 14 Extra Credit Problem 14.21 5 of 10 Part A Like sulfuric acid, selenic acid (2 Se4) is a diprotic acid that has a very large value of Kal Calculate the plH of 0.51 MH2Seo4 (K2 1.2 x 10 2). Express your answers using two decimal places. pH = Submit x Incorrect; Try Again; 5 attempts remaining Part B Calculate the concentrations of all species present in 0.51 M H2seo4 (K1.2 x 102). Express your answers using two significant figures separated by commas. Enter the concentrations of the species in the order listed below. Submit Request Answer Provide Feedback Next >

Explanation / Answer

Solution:-

H2SeO4 ----- > H+   + HSeO4^-

HSeO4^- ----- > H+ + SeO4^2-   ka2 = 1.2*10^-2

Since ka 1 is very large so the initial dissociation will give the 0.50 M H+

Now let us find the H+ using the Ka2

HSeO4^- ----- > H+ + SeO4^2-                ka2 = 1.2*10^-2

0.51 0.51 0

-x                         +x            +x

0.51-x                 0.51+x      x

Ka2 = [H+][SeO4^2-]/[HSeO4^-]

1.2*10^-2 = [0.51+x][x]/[0.51-x]

1.2*10^-2 *[0.51-x] = [0.50+x][x]

=> x^2+ 0.512x-6.12*10^-3=0

Solving for x we get

X= 0.0116

Now let us find the total [H+] and concentration of other species.

Total [H+] = 0.51 M + 0.0116 M = 0.5216 M

[HSeO4^-] = 0.51 –x = 0.51 -0.0116 = 0.4984 M

[SeO4^2-] = x = 0.0116 M

Now lets calculate the pH

pH= -log [H+]

pH= -log [0.5216]

pH= 0.283

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.