Conjugate base

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Leslie Romo 1C
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

Conjugate base

Postby Leslie Romo 1C » Sat Nov 21, 2015 11:26 pm

how do you know/calculate what conjugate base is the strongest?

ex: which of the following produces the strongest conjugate base???

HF(pKa=3.45)
CH3COOH(pKa=4.75)
HClO(pkA=7.53)
HIO(pKa=10.64)
HCOOH(pKa=3.75)

Chem_Mod
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Re: Conjugate base

Postby Chem_Mod » Sun Nov 22, 2015 4:33 am

The weaker the acid, the stronger the conjugate base. Therefore, the weakest acid will have the strongest conjugate base and the strongest acid will have the weakest conjugate base. Acids with a smaller pKa are stronger than those with a high pKa. We can then make the connection that low pKa =strong acid= weak conjugate base.

Juliana Logan 1A
Posts: 20
Joined: Fri Sep 25, 2015 3:00 am

Re: Conjugate base

Postby Juliana Logan 1A » Sun Nov 22, 2015 7:38 pm

HF(pKa=3.45) Conjugate base: F- (pKb=14-3.45=10.55)
CH3COOH(pKa=4.75) Conjugate base: CH3CO2 (pKb=14-4.75=9.25)
HClO(pkA=7.53) Conjugate base: ClO (pKb=14-7.53=6.47)
HIO(pKa=10.64) Conjugate base: I- (pKb=14-10.64= 3.36)
HCOOH(pKa=3.75) Conjugate base: HCO2 (pKb=14-3.75=10.25)

In this example, the order of strongest conjugate bases from weakest to strongest would be F-, HCOOH, CH3COOH, HClO, I-.
Therefore the acid that produces the strongest conjugate base would be HIO.


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