Can you classify acids as strong or weak from their formulas alone? [ENDORSED]

[Wesley_Rugen_1E]

Can you classify acids as strong or weak from their formulas alone?

[Justin Folk 3I]

No, usually not. The only strong acids are the ones that are listed as "strong acids," and we know this because a Ka value doesn't exist-- everything dissociates so [HA] == 0, and Ka becomes undefined.

Theoretically, you could deduce based on electronegativity its ionic vs covalent character. But just memorize the strong acids.

[Yamilex Velgara 2I]

I'm not entirely sure, but for the purpose of this class, memorize the list of strong acids. All other acids will most likely be weak acids, according to my PLF.

[Laine Gruver 3C]

Does anybody know if the list of strong acids in the course reader is exhaustive?

[Tycho_Meimban_2B]

Better to memorize the list of all strong acids and bases. I would assume that if an acid or base is not strong, then it is weak.

[divya_devineni_2E]

So does that mean for any acid or base that has a K value, we can disregard the subtracted "x" from the reactants when setting up the equilibrium formula?

[Anna Makridis_L1]

Yes, I think you are correct in assuming that because the x value would be so small anyways that it doesn't matter if you subtract it. However it is important to remember that it is still greater than 0 because if it was 0 then your numerator wouldn't make sense either.

[Chem_Mod]

So does that mean for any acid or base that has a K value, we can disregard the subtracted "x" from the reactants when setting up the equilibrium formula?

Only for K values that are less than 10^-4 as I discussed in class.
Remember to check the % product formed and if it is less than 5% of the initial reactant concentration then approximation is acceptable.

If one has an acid or base with a K = 10^-1 (for example) then X is unlikely to be less than 5%.

K will not be given for a strong acid and base. Look for this in a question if you don't recognize the acid or base as strong/weak.