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.

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

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

Well, if we break down the generic equation, we see that the base reacts with water to form a positive ion and a hydroxide ion.

1) CaI2: Calcium iodide is a salt, but when it dissolves in water, it produces Ca^2+ and 2I^- ions. It does not form any hydroxide ions, so it doesn't follow the generic equation.

2) NH3: As you mentioned, ammonia (NH3) is not a salt. It is a compound that can act as a base, but it doesn't produce any ions when dissolved in water.

3) KCN: Potassium cyanide is a salt. When it dissolves in water, it produces K^+ and CN^- ions. CN^- can react with water to form OH^- ions, which fits the generic equation.

4) Al(NO3)3: Aluminum nitrate is a salt. When it dissolves in water, it produces Al^3+ and 3NO3^- ions. NO3^- does not react with water to form OH^- ions, so it doesn't follow the generic equation.

5) NaCl: Sodium chloride is a salt. When it dissolves in water, it produces Na^+ and Cl^- ions. Cl^- does not react with water to form OH^- ions, so it doesn't follow the generic equation either.

Therefore, the only salt that fits the generic equation is KCN. I hope that clarifies things for you!

To determine which salt can be accounted for by the generic equation Base− + H2O -> HBase+ OH−, we need to identify which salt can produce a basic solution when dissolved in water.

Let's consider each option:

1) CaI2 (calcium iodide): This salt consists of a metal ion (Ca2+) and an anion (I-). When dissolved in water, it will dissociate into Ca2+ and 2I-. Neither Ca2+ nor I- is a strong base, so CaI2 cannot account for the generic equation.

2) NH3 (ammonia): You correctly pointed out that ammonia is not a salt, as it is a gas at room temperature. Therefore, NH3 cannot be accounted for by the given equation.

3) KCN (potassium cyanide): This salt contains a metal ion (K+) and a cyanide ion (CN-). Cyanide ions can act as a weak base, accepting a proton (H+) from water to produce OH-. Therefore, when KCN is dissolved in water, it can account for the generic equation by producing a basic solution.

4) Al(NO3)3 (aluminum nitrate): This salt contains a metal ion (Al3+) and nitrate ions (NO3-). Neither Al3+ nor NO3- is a strong base, so Al(NO3)3 cannot account for the generic equation.

5) NaCl (sodium chloride): This is a widely known salt that consists of a metal ion (Na+) and a chloride ion (Cl-). Neither Na+ nor Cl- is a strong base, so NaCl cannot account for the generic equation.

Based on the analysis, the correct answer is 3) KCN since it can produce a basic solution when dissolved in water, thereby fitting the generic equation Base− + H2O -> HBase+ OH−.