## Sig Figs for Calculating pH and pOH

Thuy-Anh Bui 1I
Posts: 56
Joined: Sat Jul 22, 2017 3:00 am
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### Sig Figs for Calculating pH and pOH

For calculating logarithms/pH/pOH, the number of sig figs comes from the mantissa aka after the decimal place. However, for some problems (such as 12.27 and 12.29), the solutions manual does not acknowledge this. If the calculation was pH=-log(0.025) (2 sig figs), wouldn't the answer be 1.60 with the 2 sig figs shown in the decimal place?

Alex Leve 3F
Posts: 20
Joined: Fri Sep 29, 2017 7:07 am

### Re: Sig Figs for Calculating pH and pOH

Yes, I believe you are correct about the number of significant figures that the solution should have.

Camille Ng 1D
Posts: 18
Joined: Thu Jul 27, 2017 3:01 am

### Re: Sig Figs for Calculating pH and pOH

Yes, just use the same amount of sig figs that are given in the question for your solution.

Ishan Saha 1L
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

### Re: Sig Figs for Calculating pH and pOH

1.60 actually has 3 sig figs, because all 0's after nonzero values after the decimal count as sig figs. I believe the correct answer would be 1.6, with 2 sig figs as was used in the original question.

Suhail Zaveri
Posts: 24
Joined: Sat Jul 22, 2017 3:01 am

### Re: Sig Figs for Calculating pH and pOH

Hello,

Usually the pH is calculated by counting two digits after the decimal, usually the sig figs will be counted after the decimal place so 1.66 has two significant figures.

Hope this helps

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