Ammonium, $ceNH_4^+$, is the conjugate mountain of ammonia, $ceNH_3$. I have searched the Internet and so countless different answers pop up. The ascendancy of ignorance that I review was that a strong acid has actually a weak conjugate counterpart.

For example, a solid acid has actually a weak conjugate base. Is ammonium a solid or weak acid? Is ammonia a strong or weak base? Is over there something come the dominance of ignorance that i mentioned?



Both ammonia is a weak base and also ammonium ion is a weak acid. Many, also most, acid/base conjugate bag are prefer that. We have to be making use of comparative rather of pure adjectives in the rule about conjugate acid-base strengths:

A weaker acid has a stronger conjugate base, not necessarily a totally solid one.

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A weaker base has a stronger conjugate acid, not necessarily a totally strong one.


Consider these reactions: eginequationceHA + H2O A- + H3O+ ag1endequationeginequationceA- + H2O HA + OH- ag2endequation

The equilibrium consistent for reaction (1) is dubbed "acid dissociation constant", $K_ m a$, and the 2nd is "base association constant", $K_ m b$. (Note the the names space there for historical reasons, they"re no correct, strict speaking) we can element out the water"s concentration to a great approximation in dilute solutions. Think about that

eginequationK_ m a imes K_ m b = fraccece imes fraccece = ce = K_ m w ag3endequation

$K_ m w$ is constant in continuous temperature, hence $K_ m a$ and also $K_ m b$ space inversely proportional to each other. Again, to a great approximation, us have

eginequation-logK_ m a + (-logK_ m b)=-logK_ m w: Longrightarrow m pK_ m a + m pK_ m b = 14 ag4endequation

p$K_ m a$s in between -1.7 ($ceH3O+$/$ceH2O$) and also 15.7 ($ceH2O$/$ceOH-$) are said to it is in those the weak mountain in water. Acids with $K_ m a$s in this range do not dissociate totally in water, and named weak mountain (and weak bases, for the matter1) in water.

Now, think the it choose this: $x+y=14$. If $x$ is 5, $y$ is 9, and also if $x$ is -5, $y$ is 19. (4) is whereby your ascendancy of ignorance originates from. So

A weak acid prefer acetic acid through a p$K_ m a$ of 4.76 will have a weak conjugate base through a p$K_ m b$ that $14-4.76=9.24$.A solid acid prefer $ceHCl$ through a p$K_ m a$ that -7 will have a conjugate base v a p$K_ m b$ that $14-(-7)=21$.

Thus as Oscar"s answer points out, it"s inaccurate the method your pointer is phrased, yet it"s naturally adhering to if we usage comparatives because that phrasing. I"d dare say most conjugate bases the weak acids pointed out in textbooks room weak ones.

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1: together the comment point out out, the weak base selection is p$K_ m b$>1. That slipped.