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pH

Posted: Sun Jan 26, 2020 5:28 pm
by Abigail Menchaca_1H
How would you find the pH of a solution only given the pKa?

Re: pH

Posted: Sun Jan 26, 2020 5:39 pm
by Prasanna Padmanabham 4I
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+]

Re: pH

Posted: Sun Jan 26, 2020 5:45 pm
by Callum Guo 1H
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.

Re: pH

Posted: Sun Jan 26, 2020 5:46 pm
by Hussain Chharawalla 1G
Also be careful to check whether you’re given pKa or pKb and whether you want to find OH or H+ concentration

Re: pH

Posted: Sun Jan 26, 2020 6:03 pm
by Areli C 1L
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 :)

Re: pH

Posted: Sun Jan 26, 2020 9:54 pm
by Caroline Zepecki
if you know the pka, you can use the equation PkW = PkA x PkB.

Re: pH

Posted: Sun Jan 26, 2020 10:00 pm
by Charysa Santos 4G
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.

Re: pH

Posted: Sun Jan 26, 2020 10:00 pm
by Hannah Pham
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+].