conjugates

[Jennifer Torres 2L]

why are conjugates weaker than the original acids and bases?

[Lauren Ho 2E]

This is not necessarily true. For instance, a weak acid/base will have a stronger conjugate base/acid.

[Faith Fredlund 1H]

This is called the Conjugate Seesaw. For every acid, there is a conjugate base; and for every base there is a conjugate acid. If you start with a strong base or acid, its conjugate will be weak; the reverse is also true for if you start with a weak base or acid, then it will have a strong conjugate.

This is because (Ka)(Kb)=Kw= 10^(-14).
(acidity constant)X(basicity constant)= a fixed number.
Essentially, because the acidity constant and the basicity constant have an inverse relationship, whatever is put into a solution will have an inverse effect on the outcome.

For example, if a strong acid is placed into a solution, it will dissociate completely, meaning the products are more stable than the reactants. The acid will donate essentially all of its protons. What is left is its conjugate base, which is weak because it will not readily accept another proton now that it is in a more stable state.

[Maddy Mackenzie]

yes this is due to the conjugate see saw. When the acid is very strong, then the reaction wants to proceed to the right and produce H30+. The conjugate base is then weak because the reaction favors the forward reaction and the reverse reaction (the base accepting a proton) is not favored. The base does not easily accept protons.