Standard Reduction Potential Changes in Regards to Acidity

• Teemo
In summary, using the Nernst equation, the effect on the half-cell potential at 25 °C when the pH of the solution is increased by one unit is a decrease of 59 mV. The reaction quotient would be 1, as the activity of a pure substance is 1.
Teemo

Homework Statement

The reduction of O2 to H2O in acidic solution has a standard reduction potential of +1.23 V. What is the effect on the half-cell potential at 25 °C when the pH of the solution is increased by one unit?

O2(g) + 4H+(aq) + 4e- –> 2 H2O(l)

(A) The half-cell potential decreases by 59 mV.
(B) The half-cell potential increases by 59 mV.
(C) The half-cell potential decreases by 236 mV.
(D) The half-cell potential increases by 236 mV.

Nernst Equation

The Attempt at a Solution

I'm aware this is a Nernst equation problem. Yet, I'm not exactly sure how to apply it. It appears to me that the reaction quotient would be 0, since there is only a pure liquid on the product side. As such, I am not sure how to approach the problem.

Teemo said:
quotient would be 0, since there is only a pure liquid on the product side

Activity of a pure substance is not zero.

Would it be 1? I feel like I'm missing something obvious

Yes, it is 1. Just like activity of solids (think Ksp - it doesn't contain solid, as its activity is 1).

Thank you so much!

1. What is standard reduction potential?

Standard reduction potential is a measure of the tendency of a chemical species to gain electrons and undergo reduction, compared to a standard hydrogen electrode under standard conditions.

2. How does the acidity affect standard reduction potential?

The acidity, or pH, of a solution can greatly affect the standard reduction potential. Generally, as the pH decreases (becomes more acidic), the standard reduction potential becomes more positive, indicating a greater tendency for the species to be reduced. As the pH increases (becomes more basic), the standard reduction potential becomes more negative, indicating a lesser tendency for the species to be reduced.

3. What is the relationship between standard reduction potential and acidity?

The relationship between standard reduction potential and acidity is inverse. As the standard reduction potential becomes more positive, the acidity decreases and becomes more basic. As the standard reduction potential becomes more negative, the acidity increases and becomes more acidic.

4. How do we measure the standard reduction potential changes in regards to acidity?

The standard reduction potential changes in regards to acidity can be measured through electrochemical methods, such as using a potentiometer or a voltameter. These methods involve measuring the voltage or current generated by the redox reaction under specific acidic conditions and comparing it to a standard hydrogen electrode.

5. How can standard reduction potential changes in regards to acidity be used in practical applications?

The standard reduction potential changes in regards to acidity have many practical applications, such as in corrosion prevention, electroplating, and battery technology. By understanding how the standard reduction potential changes with acidity, we can control and manipulate redox reactions to our advantage in these applications.

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