## Sig Figs for pH

Posts: 19
Joined: Wed Sep 21, 2016 2:57 pm

### Sig Figs for pH

What exactly are the sig fig rules when reporting pH?

hfrazer1B
Posts: 19
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Sig Figs for pH

Is it not the same as the other sig fig rules?

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

### Re: Sig Figs for pH

No, I don't think so. I remember learning in AP Chem that the number of sig figs you have becomes the number of decimal places in the pH value (ex. 3 sig figs = 3.000). But the textbook solutions are given in a way that the number of sig figs you have are the sig figs in the answer (ex. 3 sig figs = 3.00). I'm also not sure which rule we should use.

Anna_Kim_2E
Posts: 31
Joined: Wed Sep 21, 2016 2:56 pm

### Re: Sig Figs for pH

The previous thread says that we should,
"When working with pH, use the number of sig figs as the number of decimal places in the pH. For example, if the pH=-log(1.8 x 10^-5) then pH = 4.74 (two sig figs in 1.8 x 10^-5, and two after the decimal in 4.74)."