Ph and PKA

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Claire_Kim_2F
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Ph and PKA

Postby Claire_Kim_2F » Wed Dec 09, 2020 12:30 am

I was wondering if the pka is higher than the ph then does that mean it is neutral according to the lecture #28 where Dr.Lavelle said it is negative because the pka is lower than the ph? Also what exactly does pka mean because I thought it was strength of acid but Dr.Lavelle said if it is more acidic is has a lower pka?

Claire_Latendresse_1E
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Re: Ph and PKA

Postby Claire_Latendresse_1E » Wed Dec 09, 2020 12:43 am

Nice name! The reason that an acid is more acidic when it has a lower pKa is that pKa = -log[Ka]. An inverse relationship would form (as Ka increases, pKa decreases).
When pH < pKa (acidic conditions), the acid gets protonated as HA. It will be neutral.
When pH > pKa, the acid will give off a proton (the acid is stronger than the solution). It will have a negative charge after it gives off its proton and becomes A-.

Ivy Tan 1E
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Re: Ph and PKA

Postby Ivy Tan 1E » Thu Dec 10, 2020 2:33 pm

Hi!
Adding on to the response above, when pH < pKa, the solution is already in an acidic environment because the pH is lower, so the acid will not dissociate to make the solution even more acidic (it is neutral). When pH > pKa, the solution is in a basic environment because the pH is higher, so the acid will dissociate and become ionized. Hope this was helpful!!

Claire_Kim_2F
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Re: Ph and PKA

Postby Claire_Kim_2F » Fri Dec 11, 2020 7:23 pm

Is ha the base and a- the acid component of the equation?

Kaili Valenzuela 2B
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Re: Ph and PKA

Postby Kaili Valenzuela 2B » Fri Dec 11, 2020 7:28 pm

Claire_Kim_2F wrote:Is ha the base and a- the acid component of the equation?

Actually, HA is the acid and A- is the base

Inderpal Singh 2L
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Re: Ph and PKA

Postby Inderpal Singh 2L » Fri Dec 11, 2020 10:24 pm

HA is the acid and A- is the base!

Sofia Lombardo 2C
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Re: Ph and PKA

Postby Sofia Lombardo 2C » Sat Dec 12, 2020 5:20 pm

Claire_Latendresse_3J wrote:Nice name! The reason that an acid is more acidic when it has a lower pKa is that pKa = -log[Ka]. An inverse relationship would form (as Ka increases, pKa decreases).
When pH < pKa (acidic conditions), the acid gets protonated as HA. It will be neutral.
When pH > pKa, the acid will give off a proton (the acid is stronger than the solution). It will have a negative charge after it gives off its proton and becomes A-.


Sorry, I am just a bit confused about the charges. Like if we were comparing pOH and pKb if the pOH > pKb, would the base get a positive charge?

205323697
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Re: Ph and PKA

Postby 205323697 » Thu Dec 17, 2020 8:55 am

How do we get from pH to pKa?


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