pH

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Abigail Menchaca_1H
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

pH

Postby Abigail Menchaca_1H » Sun Jan 26, 2020 5:28 pm

How would you find the pH of a solution only given the pKa?

Prasanna Padmanabham 4I
Posts: 111
Joined: Thu Jul 25, 2019 12:17 am

Re: pH

Postby Prasanna Padmanabham 4I » Sun Jan 26, 2020 5:39 pm

It really depends on what information you are given, I feel like for most problems this is how I've been dealing with it...
1) convert pKa to Ka
Ka = 10^(-pKa)
2) write Ka concentration out and figure out [H+]
3) plug into pH = -log [H+]

Callum Guo 1H
Posts: 134
Joined: Fri Aug 02, 2019 12:15 am
Been upvoted: 1 time

Re: pH

Postby Callum Guo 1H » Sun Jan 26, 2020 5:45 pm

You would probably take the 10^-pka to convert it into Ka and then make a ICE table to find the concentration of H+ ions. After that, you would take the -log of the H+ concentration.

Hussain Chharawalla 1G
Posts: 100
Joined: Sat Jul 20, 2019 12:15 am

Re: pH

Postby Hussain Chharawalla 1G » Sun Jan 26, 2020 5:46 pm

Also be careful to check whether you’re given pKa or pKb and whether you want to find OH or H+ concentration

Areli C 1L
Posts: 95
Joined: Wed Nov 14, 2018 12:19 am

Re: pH

Postby Areli C 1L » Sun Jan 26, 2020 6:03 pm

Prasanna Padmanabham 4I wrote:It really depends on what information you are given, I feel like for most problems this is how I've been dealing with it...
1) convert pKa to Ka
Ka = 10^(-pKa)
2) write Ka concentration out and figure out [H+]
3) plug into pH = -log [H+]

I like this, clear and not too wordy :)

Caroline Zepecki
Posts: 101
Joined: Fri Aug 09, 2019 12:16 am

Re: pH

Postby Caroline Zepecki » Sun Jan 26, 2020 9:54 pm

if you know the pka, you can use the equation PkW = PkA x PkB.

Charysa Santos 4G
Posts: 107
Joined: Wed Sep 18, 2019 12:21 am

Re: pH

Postby Charysa Santos 4G » Sun Jan 26, 2020 10:00 pm

If they give you the pKa, they would likely also have given the concentration of either [OH-] or [H3O+] or you would have to solve for them, and then you could use that value to do -log([H3O+]/[OH-]) and find the pH/pOH.

Hannah Pham
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

Re: pH

Postby Hannah Pham » Sun Jan 26, 2020 10:00 pm

You could convert pKa to Ka, then use Ka = 10^(-pKa). Use the Ka to find [H3O+]. Determine pH by this equation: pH = -log [H3O+].


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