Going from pKa to pH

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ursulavictorino1K
Posts: 55
Joined: Sun Feb 17, 2019 12:15 am

Going from pKa to pH

Postby ursulavictorino1K » Sun Feb 23, 2020 8:36 pm

I'm still quite confused on how to go from pKa to pH like it was asked on one of the midterm questions. Could someone break it down?

Vinita Saxena 2I
Posts: 58
Joined: Fri Aug 09, 2019 12:16 am

Re: Going from pKa to pH

Postby Vinita Saxena 2I » Sun Feb 23, 2020 8:38 pm

Use pKa to get the concentration of H3O+ (using an ice table) and then use the concentration of H3O+ to get the pH

Alondra
Posts: 36
Joined: Tue Feb 26, 2019 12:15 am

Re: Going from pKa to pH

Postby Alondra » Sun Feb 23, 2020 9:35 pm

The image I attached explains the relationship between pka,pkb,pH and pOH.
Attachments
Summary+of+Mathematical+Relationships.jpg

ursulavictorino1K
Posts: 55
Joined: Sun Feb 17, 2019 12:15 am

Re: Going from pKa to pH

Postby ursulavictorino1K » Sun Mar 01, 2020 11:41 pm

I was confused because in my notes u had pka=10^7 and pH=7 so I don't know if I miswrote it.

J Medina 2I
Posts: 102
Joined: Wed Sep 25, 2019 12:17 am

Re: Going from pKa to pH

Postby J Medina 2I » Sun Mar 01, 2020 11:44 pm

Maybe you meant that when pKa = 10^-7 that the pH = 7, which would be true.

WGaines_2E
Posts: 47
Joined: Mon Nov 18, 2019 12:18 am

Re: Going from pKa to pH

Postby WGaines_2E » Mon Mar 09, 2020 9:13 pm

The lower the pH, the higher the concentration of hydrogen ions [H+].
The lower the pKa, the stronger the acid and the greater its ability to donate protons.

Sally Qiu 2E
Posts: 105
Joined: Fri Aug 30, 2019 12:18 am

Re: Going from pKa to pH

Postby Sally Qiu 2E » Mon Mar 09, 2020 9:16 pm

i don't believe there's any direct conversion to get from pKa to pH. instead you'll have to convert pKa to Ka and make an ICE table to find the concentration of H+. then you can solve the equation and convert H+ to pH.

Subashni Rajiv 1K
Posts: 101
Joined: Wed Sep 18, 2019 12:16 am

Re: Going from pKa to pH

Postby Subashni Rajiv 1K » Mon Mar 09, 2020 9:52 pm

Also, don't forget that pKa and pKb are related to one another. So if you are given the pKb and asked for pH you can convert to pKa and go from there.

Jacob Motawakel
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Joined: Wed Sep 18, 2019 12:20 am
Been upvoted: 1 time

Re: Going from pKa to pH

Postby Jacob Motawakel » Mon Mar 09, 2020 10:07 pm

You can use pKa to find the concentration of [H+] through an ICE box, then using the [H+] concentration, you can find pH by plugging [H+] into the equation pH=-log[H+]

Julia Holsinger_1A
Posts: 50
Joined: Tue Feb 26, 2019 12:16 am

Re: Going from pKa to pH

Postby Julia Holsinger_1A » Wed Mar 11, 2020 4:43 pm

What does the w in pKw stand for?

William Chan 1D
Posts: 102
Joined: Sat Sep 14, 2019 12:15 am

Re: Going from pKa to pH

Postby William Chan 1D » Wed Mar 11, 2020 10:17 pm

^above, the w stands for water. kw is the equilibrium constant for water at 25°C.

For the actual question, from pka, we can determine ka. Using ka, we can use an ice table, using the initial concentrations of the reactants and products to determine the [H+] concentration, and using [H+], we can determine pH.


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