Weak Acids/Bases and conjugate Bases/acids

[Ashley Chipoletti 1I]

Why is it that weak acids have strong conjugate bases and vice versa for weak bases and their conjugate acids?

[Sara Varadharajulu]

general info:
a high value of ka or kb correlates with a strong acid or base since the products are heavily favored. a low value of ka or kb correlates with a weak acid or base since the reactants are favored.
ka*kb=Kw=10^-14

If its a weak acid, then its ka will be quite small; because Ka*Kb equals Kw (10^-14), the kb for the conjugate base will be quite large. this means that even though the acid is weak and has a small ka, the conjugate base is strong as it has a large kb.
same applies to a weak base. if you have a weak base, you have a small value for kb, which means the value for ka for its conjugate acid is large; this means that the conjugate is strong.

hope this helps!

[Michelle Lee 2E]

We know that Ka(Kb) = 10^-14
Kw=10^-14 is a constant so it doesn't change. Therefore, if Ka is small, Kb must be larger to compensate. Vice Versa, if Kb is small, Ka must be larger to compensate.
This is like when we learned c=v(lambda). The speed of light is constant. If frequency is higher, the wavelength is shorter and vice versa.

[Sarah Brauer]

Do strong acids have weak conjugate bases?