Use this equilibrium equation to complete the next question: 4 SO4^2- + 4 Co^3+

Question

Use this equilibrium equation to complete the next question: 4 SO4^2- + 4 Co^3+ <---> S2O8^2- + 4Co^2+
If the equilibrium constant is 9*10 ^-9 Find all concentrations of the initial Co^3+ concentration is 0.5 M and the initial SO4^2- concentration is 0.3 M Use this equilibrium equation to complete the next question: 4 SO4^2- + 4 Co^3+ <---> S2O8^2- + 4Co^2+
If the equilibrium constant is 9*10 ^-9 Find all concentrations of the initial Co^3+ concentration is 0.5 M and the initial SO4^2- concentration is 0.3 M
If the equilibrium constant is 9*10 ^-9 Find all concentrations of the initial Co^3+ concentration is 0.5 M and the initial SO4^2- concentration is 0.3 M

Explanation / Answer

Well, first of all lets rewrite the equation , as it is wrong balanced the way you wrote it. The equation correctly balanced is:

2 SO4-2 + Co+3 <--------> Co+2 + S2O8-2   

now, it is useful to write the equilibrium constant for this reaction:

K = [Co+2]  [S2O8-2 ] / [SO4-2 ]2 [Co+3]= 9x10-9

The best here is to use the ICE method:

[SO4-2 ] : initial: 0.3M , change: -2X, equilibrium: 0.3M - 2X

[Co+3] : initial: 0.5M , change: -X , equilibrium: 0.5M - X

[Co+2]: initial: 0 , change: X, equilibrium: X

[S2O8-2 ]: initial: 0, change: X , equilibrium: X

Now we rewrite the equilibrium constant replaceing the equilibrium concentrations.

K = [Co+2]  [S2O8-2 ] / [SO4-2 ]2 [Co+3]= 9x10-9 = X* X / (0.5M-X ) (0.3M-2X)2

X2 / (0.5 - X) (0.09 - 0.12X + 4X2) =  9x10-9

X2 /(0.045 - 0.06X - 0.09X - 2X2 + 0.12X2 - 4X3 =  9x10-9

0.045 - 0.06X - 0.09X - 2X2 + 0.12X2 - (1/ 9x10-9 )X2 - 4X3 = 0

- 4X3 -111111112 X2 - 0.15X + 0.045 = 0

The roots of the polynomial are:

x1=2.0E?5

x2=?2.0E?5

x3=?27777778

As the X cannot be a negative number, X = 2x10-5 . Then:

[SO4-2 ] : equilibrium: 0.3M - 4x10-5

[Co+3] : equilibrium: 0.5M - 2x10-5

[Co+2]: equilibrium: 2x10-5

[S2O8-2 ]:equilibrium: 2x10-5

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

---

---

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