# Solving for electron activity given pH and ratio of redox elements

• Chemistry
• peeballs
In summary, the conversation discusses the equilibrium statement for the half reaction 8e- + 9H+ + SO42- = HS- + 4H2O, with a logK value of 4.25. The participant is solving for the unknowns x and e- using the given expression, but is unsure of how to proceed. They were able to get clarification from another source.
peeballs
Homework Statement
What is the apparent pO2 (atm) in equilibrium with a pE governed by the sulfate/sulfide redox buffer when
(SO4
2-) = 10x (HS-) at paH 8.2? Use constants from Table 8.6a, pg. 465, assume I=0.
Relevant Equations
K = Products/Reactants
I've written out the half reaction

8e- + 9H+ + SO42- = HS- + 4H2O

and I know the logK = 4.25 (that's the constant mentioned in the prompt)

I've written out the equilibrium statement of 10^4.25 = ([x^1/8]*[H2O^1/2])/([10x^1/8]*[e-]*[(10^-8.2)^9/8]

However, from there, it seems like I have two unknowns - the X, and the e-, which I'm solving for. I don't know of any formulas that would be useful here and I was specifically told to use this expression to solve it.

Thanks

You sure x is an unknown, and not a multiplication sign?

Borek said:
You sure x is an unknown, and not a multiplication sign?
Yes, but you managed to find me on a different forum and explain why I was having a brainfart so it all works out.

## 1. What is the relationship between electron activity, pH, and the ratio of redox elements?

The electron activity, or the tendency of an element to gain or lose electrons, is directly related to the pH and the ratio of redox elements in a solution. As the pH increases, the electron activity decreases, making it more difficult for an element to gain or lose electrons. Similarly, a higher ratio of redox elements means there are more potential electron donors or acceptors, leading to a higher electron activity.

## 2. How do you calculate the electron activity given pH and the ratio of redox elements?

The electron activity can be calculated using the Nernst equation, which takes into account the pH and the ratio of redox elements. The equation is: E = E° - (0.0592/n)log(Q), where E is the electron activity, E° is the standard potential, n is the number of electrons transferred in the redox reaction, and Q is the reaction quotient.

## 3. Can the electron activity be directly measured in a solution?

No, the electron activity cannot be directly measured. It is a calculated value based on the Nernst equation and the concentrations of the redox elements in the solution. However, the potential of the solution can be measured using a pH meter or a redox electrode, which can then be used to calculate the electron activity.

## 4. How does temperature affect the electron activity in a solution?

The Nernst equation includes a temperature term, indicating that the electron activity is affected by temperature. As the temperature increases, the electron activity also increases, making it easier for elements to gain or lose electrons. However, this effect is relatively small and is usually only significant at extreme temperatures.

## 5. What is the significance of knowing the electron activity in a solution?

The electron activity is an important factor in understanding the redox reactions occurring in a solution. It can help predict the direction and rate of a reaction, as well as the potential for corrosion or other chemical processes. Additionally, knowledge of the electron activity can aid in the design and optimization of industrial processes and environmental remediation strategies.

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