acid, base, how much do we need to know?

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joonkimdds

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What I memorized are
6 strong acids: HClO4>HI>HBr>HCl>H2SO4>HNO3
inc down the periodic table: HI>HBr>HCl>HF
electronegativity matters in same row: HF>H2O>NH3>CH4
More O is more acidic: H2SO4>H2SO3
More H is more acidic: NH4>NH3>NH2
strong acid has weak conjugate base: HClO4 is strong acid, ClO4- is weak base

these are what I know
I was wondering what else I should know to prepare for all the "which is stronger/weaker acid/base" type of questions.


Also, based on what I know, I was doing destroyer #69.
HClO4 > OH- > NH3 > NH2- > ClO4-
I think this should be the order of acidity.
But the solution says OH- and NH2- are strong bases, NH3 is a weak base.
When I compare O and N, O is more electronegative so I think O should be more acidic than NH3 and NH2. I don't know why OH- is a stronger base than NH3.

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OH is a charged molecule that is very unstable. NH3 is an uncharged stable ammonia molecule. Why should tyhe stable molecule that has an octet be less stable than OH- which has a charge.
 
OH is a charged molecule that is very unstable. NH3 is an uncharged stable ammonia molecule. Why should tyhe stable molecule that has an octet be less stable than OH- which has a charge.

Does stability has anything to do with acidity?
 
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