pKa and pH [ENDORSED]

[Xinyue Zou 2K]

I'm a little confused on the relationship between pKa and pH for acids and bases and what it means when the pH is larger or lower than the pKa value for both acids and bases. Could someone help clarify how to tell if it's charged, neutral, or unknown?
Thank you!

[Briana Chavez 3F]

Hi! From what I understand, pKa is the dissociation of an acid, and pH is the acidity/alkalinity of the whole experiment. When pH and pKa are equal to each other, it means that the concentration of the conjugate acid and conjugate base are also equal. I believe that when the pH increases, so does the proportion of the conjugate base, etc.

[KPINTO 1B]

Hi! So, in chem 14a, my TA taught me that if you break down pH to H3O+ and pKa into the acid equilibrium expression, with H3O+ and A- on top, and HA on the bottom, you could then solve for what the relationship means. But, to put it in simple terms, if pH is greater than pKA, then it is charged because there is more A- than HA, but if pKA is larger than pH then its neutral because it is more stable if it does not dissociate, so there is more HA then A-. I hope this helps!

[Kimia Rategh 2A]

Hi! When comparing the pka to the pH we are indicating which direction the reaction will shift towards. If the pka is greater than the pH, then the production of the acid will be favored. Depending on whether or not the reaction is an acid (uncharged) reaction with water or if a base reacts with water to produce a conjugate acid (charged), then you would tend to the uncharged or charged particle respectively. If the pka is less than the pH, the production of the base (either conjugate or not) is favored. So if the reaction is a base reacting with water (uncharged), or an acid reacting with water to provide a conjugate base (charged), the reaction where the pka is less than the pH would result in the favoring of either the uncharged or charged particle respectively.

Hope this helps!

[emmakvarnell]

pKa is the -log of the equilibium constant, while pH is the -log of the Hydronium concentration.

[Chem_Mod]

Everyone see the new resource I created to assist students with key concepts in titrations, buffers, the relationship between pH and pKa, and determining if an acid or base is ionized.

Concepts in titrations, buffers, etc.
https://lavelle.chem.ucla.edu/wp-conten ... ns_etc.pdf

[JasmineReyes-2K]

Hi!,

I think pKa is our -log of the equilibrium constant (K) while pH is the acidity of the whole equation which is -log of the Hydronium concentration

[Morgan Micallef 1A]

I was also confused about this! For weak acids, if pH is greater than pKa, there is more of the charged species; if pKa is greater than pH, there is more of the neutral species. For weak bases, the opposite is true.

[Jennifer Fuentes 2K]

The lower the pH, the higher the concentration of hydrogen ions [H+]. The lower the pKa, the stronger the acid and the greater its ability to donate protons. pH depends on the concentration of the solution. This is important because it means a weak acid could actually have a lower pH than a diluted strong acid.

[Emily Wu 2G]

pH determines how acidic or basic something is, and pKa is the -log of pH

[kareena_prasad]

pKa is the equilibrium constant and pH is the concentration of hydronium.

[Ashley Gonzalez Dis 2A]

Hi! pH is the measure of the concentration of hydrogen ions while pKa is the acid dissociation constant. pKa helps you identify what the pH needs to be to accept or donate a proton. Lower pKa = stronger acid and greater ability to donate a proton and higher pKa= stronger base and greater ability to accept a proton

[dericasu3a]

pKa is the negative log of the equilibrium constant. pH is the negative log of the hydronium concentration.

[Cynthia_L_2C]

From my understanding, pH is the negative log of the hydronium concentration, and pKa is the negative log of the equilibrium constant.

[Daniela G 2C]

The lower the pKa -> the stronger the acid
The lower the pH -> the higher of [H+]

[kayleec1004]

When the pKa is low then the acid is strong.
When the pH is low then [H+] is high.

[almaortega]

If the pH is greater than the pKa value, there is more [A-] but if the pKa is greater, there's more [HA]. It is also true that when the pKa is low, it is a strong acid. When the pH is low then [H+] is high.

[Uma Patil 2A]

pH is the -log[H], while pKa is -log([A-][H3O+]/[HA]). As acids get stronger, pH gets lower, and pKa gets lower.

[005502505]

A lower pH means more hydrogen [H+] ions; the lower the pH, the lower the pKa. Hope this helps!

[ThomasL1L]

So pH and pKa in an equilibrium solution should be equal but if the pKa is less than the pH then it means that there is more acid being dissociated than usual while when the pKa is higher than the pH that means that there is less acid being dissociated.

[Michelle Gong]

Hello!

pKa is an equilibrium constant and pH is an indication of hydrogen ion content in any solution. In an equation, pKa will be equal to the product of [H+][A-] divided by [HA]. pKa is also equal to the negative log of pH. So, in other words, pH can be viewed as a measurement of concentration and pka the determination of how strong an acid is/what it takes for it to completely dissociate - it can also be seen as the effect of pH in a system.

Hope this helps :)

[Grace_Wu]

Hi!
pH is the indication of the acidity of a substance. This is also a measurement for the concentration of OH- and H3O+. When pKa<pH, the solution is acidic, and vise versa. These terms are both for the equilibrium of a system.

[405825570]

pH determines how acidic/basic a solution is (it is the -log of the H+ ion concentration), and pKa is the -log of the Ka value

[Om Patel]

for acids when the ka is large and the pka is smaller it means that it is more acidic

[Santiago Cortes 2J]

When the pH is lower we usually associate it with a stronger acid. When the pH is higher we associate it with a weaker acid.

[Ameen Shaheen 2I]

pH=pKa at when acids and bases are at equivalence point. In general, when pH is lower, it signifies a strong acid while a higher-ish pH number signifies a weak acid. pKa also works in a similar fashion to pH as pKa+pKb=14 similar to pH+pOH=14

[daniellediem1k]

If the pH = the pKa, then the solution is at the equivalence point. When the pH is low, it is. a strong acid, and when its higher its considered a weaker acid

[Omeed Kalan]

Similar to pKa, when the pH is low, it is a strong acid, and when its high its weak

[Diego Salgues 2K]

From what I understand pH is the -log of the hydronium concentration. pKa is the -log of the equilibrium constant. pH shows how many ions are in a solution, while pKa shows more how the relationship between products and reactants of an acid reaction are.

[Joseph Lee]

pH really only factors in the H+ concentration while the pKA will look at the entire equilibrium reaction.

[Edriana J Altea 2G]

I agree with the comments above explaining the relationship between pKa and pH, but to add, when the pKa level is low, the stronger the acid becomes and the greater the ability to donate a proton.

[005532550]

pKa is the disassociation constant for a given proton, pH is the parts of H+ in solution. pH is part of the equilibrium expression for pKa

[Tylina Guo 1K]

I also believe that the lower the pH and pKa, the stronger the acid in both cases.

[Zoe Staggs 3B]

While pH is the measure of the H+ concentration (negative log of H+ molarity), pKa is another way of measuring the acid dissociation constant (negative log of Ka). Ka measures the dissociation of an acid, so a higher Ka value indicates more dissociation and a stronger acid. If the pH is greater than the pKa, the solution is more basic and the charged, deprotonated species is predominant. If the pH is less than the pKa, the solution is more acidic, and the neutral, protonated species is favored.