pH Calculation explanation

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Sydney Pell 2E
Posts: 100
Joined: Wed Sep 11, 2019 12:17 am

pH Calculation explanation

Postby Sydney Pell 2E » Sun Dec 01, 2019 8:20 pm

Can someone explain why you have to take the negative log of the H+ concentration to find pH? Why is it negative?

KDang_1D
Posts: 127
Joined: Fri Aug 30, 2019 12:15 am
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Re: pH Calculation explanation

Postby KDang_1D » Sun Dec 01, 2019 8:25 pm

Concentrations for H3O+ (and OH-) are very small, so they will have a negative exponent in their molarity value. For example: [H3O+] = 1x10^-7 M. Since logarithms calculate the value of the exponent, log[H3O+] = -7. Negative numbers aren't as nice to work with as positives, so we just add the negative in front of the log to get a pH of 7.


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