## Calculating pH

$E_{cell} = E_{cell}^{\circ}-\frac{RT}{nF}\ln Q$

Nick_Kopooshian_3C
Posts: 12
Joined: Fri Jul 22, 2016 3:00 am

### Calculating pH

How do you calculate pH by using the nernst equation?

Cindy Flores 2C
Posts: 27
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Calculating pH

I have the same question! The textbook example was confusing (pg 590-591).

Miya McLaughlin 2B
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Joined: Wed Sep 21, 2016 2:57 pm
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### Re: Calculating pH

It's helpful to look at the nernst equation like this:

Ecell = E - (RT/nF) ln([P]/[R])

Here is an example, from the homework:
H2(g) + Hg2Cl2(s) --> 2H+(aq) + 2Cl-(aq)
For this equation, the value you'd be taking the ln of would look like this

ln( [H+]2 [Cl-] / [H2] )

To find the pH value, you would need to solve for [H+]. Once you know the concentration of H+ you can calculate the pH value by taking the -log[H+].

If a question is asking for the pH value, then it should provide you with the rest of the information or how to calculate it, such as Ecell, E, n and all the other concentrations. This will allow you to plug them into the equation and solve for [H+].

Miya McLaughlin 2B
Posts: 24
Joined: Wed Sep 21, 2016 2:57 pm
Been upvoted: 1 time

### Re: Calculating pH

I made a mistake when writing ln. [Cl-] should be squared.

ln( [H+]2 [Cl-]2 / [H2] )

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