Finding pH of solution knowing E°....

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In summary, the pair Ni2+/Ni has an E° of -0.25V and in order for a nickel bar immersed in a solution to not produce hydrogen, the minimum pH of the solution must be greater than 8.46. The concentration of Ni2+ is not needed as long as the potential is given.
  • #1
RaamGeneral
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Homework Statement


The pair Ni2+/Ni has E°=-0.25V. Find the minimum pH of the sulution so that a nickel bar immersed in it, doesn't produce hydrogen.

Homework Equations


-

The Attempt at a Solution


This problem doesn't make any sense to me. Maybe there is a cell in which the following reaction occurs:
2H+ + Ni ---> Ni2+ + H2

I thought I could use something like the Nernts equation but I don't know [Ni2+].

I need some guidance. Thank you.
 
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  • #2
You don't need concentration of Ni2+ if the potential is given. Actually even the identity of the metal doesn't matter.
 
  • #3
Ok, this is what I get:

-0.0591/2 * log( 1/[H+]2 ) + 0.25 < 0 [the reaction does not occur and hydrogen is not produced]
pH > 8.46
 

What is the formula for finding the pH of a solution knowing E°?

The formula for finding the pH of a solution knowing E° is pH = -log[H+], where [H+] represents the concentration of hydrogen ions in the solution.

How do I determine the concentration of hydrogen ions in a solution using E°?

To determine the concentration of hydrogen ions, you can use the Nernst equation: [H+] = 10^(-pH) = 10^(E°/0.0592), where E° is the standard reduction potential.

Can I use E° values from a table to calculate the pH of a solution?

Yes, you can use E° values from a table, but make sure they are for the same reaction and have the same units. Also, remember to consider the coefficients of the reaction when using E° values.

What is the relationship between E° and pH?

E° and pH are inversely related. As E° increases, the pH decreases, and vice versa. This is because as the reduction potential becomes more positive, the concentration of hydrogen ions decreases, resulting in a higher pH.

How does temperature affect the calculation of pH using E°?

Temperature can affect the value of E° and, therefore, the calculation of pH. Make sure to use the correct E° value for the temperature at which the reaction is occurring. Additionally, pH is temperature-dependent, so it is important to consider temperature when calculating the pH of a solution.

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