Calculating pH

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Andrea_Torres
Posts: 98
Joined: Sun Sep 15, 2019 12:15 am

Calculating pH

Postby Andrea_Torres » Sun Dec 01, 2019 6:46 pm

How do we calculate the pH of acids and base? I know there is log involved but I don't get how to use it.

Jessica Booth 2F
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Calculating pH

Postby Jessica Booth 2F » Sun Dec 01, 2019 6:48 pm

To calculate the pH of a solution take the -log of the concentration of H3O+ ions.

Akshay Chellappa 1H
Posts: 59
Joined: Wed Sep 11, 2019 12:15 am

Re: Calculating pH

Postby Akshay Chellappa 1H » Sun Dec 01, 2019 6:48 pm

To find the pH you take the negative log of the hydrogen ion concentration of a solution.

JohnWalkiewicz2J
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am
Been upvoted: 1 time

Re: Calculating pH

Postby JohnWalkiewicz2J » Sun Dec 01, 2019 6:54 pm

Typically, you take the negative log of the H+ ion concentration: pH = -log([H+])
Ex: Calculate the pH of 0.040 M HCL
- [H+] = 0.040
- -log([0.040])
- = 1.4

MKearney_4G
Posts: 50
Joined: Fri Aug 30, 2019 12:18 am

Re: Calculating pH

Postby MKearney_4G » Sun Dec 01, 2019 7:05 pm

When it is a strong acid, it's pretty straight forward: just take -log([H+]).
When it is a weak acid, then you need to do math to figure out how much H+ there will be, since it's not just the same as the original amount of acid. For weak acids you use basically the quadratic formula.

If X = [H+] and C = [HB] (original thing), then kA = ax^2 / (C-x). Solve for x and you got it!


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