### Sig Figs for logarithmic funcitons

Posted:

**Sun Dec 01, 2019 8:42 pm**How do sig figs work on logarithmic functions when doing pH calculations?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=63&t=53838

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Posted: **Sun Dec 01, 2019 8:42 pm**

How do sig figs work on logarithmic functions when doing pH calculations?

Posted: **Sun Dec 01, 2019 10:36 pm**

I'm sure the number of sig figs would be the same as the concentration that is given

Posted: **Mon Dec 02, 2019 6:33 pm**

Sig fig rules are standard for any kind of problem

Posted: **Tue Dec 03, 2019 10:31 am**

Actually, the sig figs for pH are a little different than normal. Essentially, if you are calculating the pH from a given concentration, the number of sig figs in the concentration is the number of sig figs you put AFTER the decimal point in the pH.

For example, if I was given a 3.14 * 10^{-2} M solution of HCl, I would find the pH to be 1.503. This is because the concentration has 3 sig figs so I would need 3 digits AFTER the decimal point on my pH. The 1 in front of the decimal does not count.

For example, if I was given a 3.14 * 10

Posted: **Tue Dec 03, 2019 10:35 am**

When you get the concentration and are trying to solve the pH, you would count how many sig figs the concentration has so for your answer, that would be the amount of numbers after the decimal point in your pH.

Posted: **Sat Dec 07, 2019 9:48 pm**

count the sig figs AFTER your decimal :)

Posted: **Sat Dec 07, 2019 10:17 pm**

I believe sig figs are also counted after the decimal when provided a pH and you are asked to give some numerical number, say a concentration for example. It was briefly mentioned by my TA.