Anions of weak acids give that equation for which KCN is an example (HCN is the weak acid).
CN^- HOH ==> HCN + OH^-
Other anions of weak acids such as acetic acid (acetate ion), CO3^2- etc do the same thing.
NO3^- can't work because HNO3 is not a weak acid.
NaCl can't work because HCl is a strong acid.
CaI2 can't work because HI is a strong acid.
Of course NH3 is not a salt as you point out. By the way this reaction the EXACT equation used to calculate the pH at the equivalence point of a strong base and weak acid; i.e., when NaOH and acetic acid reach the equivalence point what do you have?. That's sodium acetate, the acetate hydrolyzes to give the OH^- and the pH then is abouat 8.5 or so and NOT pH of 7 as it is with a strong base/strong acid such as NaOH/HCl.
On the other side of the coin we have salts whose cations (not anions this time) of weak bases hydrolyze also like this.
NH4Cl gives the NH4.
NH4^+ + H2O ==> H3O^+ + NH3 so these solutions are acidic as opposed to the anions above that are basic.
Salts like NaCl, KCl, KNO3 etc are neutral because NEITHER the anion nor the cation hydrolyze.
Salts like NH4C2H3O2 (ammonium acetate) that are salts of a weak base AND a weak acid may be neutral, acidic, or basic depending upon which K (Ka or Kb) is stronger.
Those are the four types of hydrolysis equations of salts that give acidic, basic, or neutral solution
The generic equation: Base− + H2O -> HBase+ OH− can be used to account for the pH of which salt? 1)CaI2 2)NH3 3)KCN 4)Al(NO3)3 5)NaCl
Ok, so I know NH3, won't work because it is not a salt. The answer is KCN, but I don't understand why, could you explain, why the other choices couldn't possibly be the answer? Thanks so much.
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How can you tell if a salt is neutral? Like the examples you gave: NaCl, KCl and KNO3, how do you know their anions or cations won't hydrolyze
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