pKa vs. regular pH

[Kathleen Vo 1G]

This may be a simple question but I just need clarification. Are pKa and pH the same thing? And is pKb and pOH the same? And if not, what is the difference? The reason why I need explanation on any difference between the two is because I see them to have similar identities where both pKa and pKb add up to 14, and pH and pOH do as well.

[hiranya sundar 2D]

So pKa and pH are not the same, and pKb and pOH are also not the same.
However, they are sort of related:
pKa = -log([A-][H+]/[HA]) where as pH is just -log[H+].
pKa takes into account the concentrations of the deprotonated and initial species, where as pH is just hydronium concentration.

pKb = -log([HA+][OH-]/[A]) where as pOH is just -log[OH-].
pKb takes into account the concentrations of the protonated and initial species, where as pOH is just hydroxide ion concentration.

That's why, on achieve, there was a problem that asked if pH is greater than pKa, is the species is charged because there is a higher hydronium ion concentration.

[Jenny Tran 2B]

No, pH and pKa are not the same.

pKa tells you if an acid is a strong acid or a weak acid. the larger the pKa, the weaker the acid.

pH will tell you if the solution is acidic or basic. pH < 7 indicates acidity, pH = 7 indicates neutrality, pH > 7 indicates a base.

on the other hand, pKb is used to measure the strength of the base. pKb is used for the dissociation of bases. similar to pKa, a larger pKb indicates a weaker base.

pOH is the measure of the hydroxide ion concentration of a solution. pOH is also used to indicate the acidity or alkalinity of a solution.

[005966393]

No they aren't the same. pH is just the -log[H+] and pKa is the -log of the entire Ka expression, which includes [H+], so they wouldn't be the same. The same goes for pOH and pKb