Sig figs in pH

Moderators: Chem_Mod, Chem_Admin

Sophia_Kiessling_2L
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

Sig figs in pH

Postby Sophia_Kiessling_2L » Sun Jan 20, 2019 12:02 pm

How do you figure out how many sig figs you are supposed to have in your final answer if being asked to calculate pH?

Jenna Salas 2H
Posts: 30
Joined: Fri Sep 28, 2018 12:22 am

Re: Sig figs in pH

Postby Jenna Salas 2H » Sun Jan 20, 2019 12:10 pm

When calculating pH, the whole number doesn't count as a sig fig only the decimal places do. For example, if your concentration of H3O+ has two sig figs, then your pH should have two decimal places.

Arshiya
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 1 time

Re: Sig figs in pH

Postby Arshiya » Sun Jan 20, 2019 12:12 pm

Depending on the significant figures of the data given in the problem, you will have that many sig figs after the decimal for pH. For example say if you were given a K value of two significant figures a potential pH value could be 2.88. You can double check on the website under everything about sig figs.

Christopher Anisi 2K
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

Re: Sig figs in pH

Postby Christopher Anisi 2K » Sun Jan 20, 2019 1:56 pm

I would say typically when using sig figs in regard to pH having 3 sig figs is standard when presenting your final answer.

Harshita Talkad 4L
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Re: Sig figs in pH

Postby Harshita Talkad 4L » Sun Jan 20, 2019 2:34 pm

The number of sig figs in the H3O+ concentration is the how many numbers there should be after the decimal place in the pH value.

beckyolmedo1G
Posts: 34
Joined: Fri Sep 28, 2018 12:21 am

Re: Sig figs in pH

Postby beckyolmedo1G » Sun Jan 20, 2019 2:51 pm

Dr. Lavelle has 2 links on his website that explain sig figs. It also shows good examples that might be helpful, if you need more clarification.

Sapna Ramappa 1J
Posts: 63
Joined: Fri Sep 28, 2018 12:24 am

Re: Sig figs in pH

Postby Sapna Ramappa 1J » Sun Jan 20, 2019 4:06 pm

If you're being asked to find pH, make sure to see how many sig figs are in the initial number. The final answer should have the same number of decimal places as the number of sig figs in the initial number.

Mukil_Pari_2I
Posts: 87
Joined: Fri Sep 28, 2018 12:29 am

Re: Sig figs in pH

Postby Mukil_Pari_2I » Sun Jan 20, 2019 4:10 pm

For pH, the sig figs in the final answer are calculated based off the least amount of sig figs in the answer. Then that amount of sig figs is used after the decimal point.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 2 guests