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Ka calculations

Posted: Mon Dec 03, 2018 8:49 pm
by Germar G 4F
Can someone explain why having a higher Ka makes a stronger acid?

Re: Ka calculations

Posted: Mon Dec 03, 2018 10:39 pm
by julia_lok_2K
If you look at Ka = ([A-][H+])/[AH], a higher Ka value denotes higher concentrations of [A-] and [H+], which means the acid has become more ionized/dissociated. Therefore, a higher Ka value makes a stronger acid.

Re: Ka calculations

Posted: Mon Dec 03, 2018 10:42 pm
by Atul Saha 3D
[x] = molarity of x

Ka = [Anion (A)] [H+] / [HA]

Take HCl. The more HCl dissociates into H+ and Cl- (the anion), the more acidic it is. Because it dissociates almost completely, the numerator of the Ka, which is [A]*[H+] will be much higher than the denominator ( the concentration of the acid that did not dissociate), creating a high Ka value. Inversely when the acid does not dissociate to such a large degree, the denominator is much bigger, yielding a smaller Ka value.