Salt Q

[tizom]

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Which of the following salts will form a pH < 7 ?

NH4NO2
NaCl
AlCl3
LiBr
Na2CO3
FeCL3

or more than one

i know the answer, but i am having trouble figuring out why. please explain!

 

[PooyaH]

Which of the following salts will form a pH < 7 ?

NH4NO2
NaCl
AlCl3
LiBr
Na2CO3
FeCL3

or more than one

i know the answer, but i am having trouble figuring out why. please explain!

Isn't it AlCl3? Just react each one with water!
AlCl3 + H2O -> Al(OH)3 + HCl (you know HCl is very acidic and Al(OH)3 is a weak base) so the pH would be less than 7
The rest of them would give you strong acid and strong base (except the last one) which would give a pH of 7!
If the question asked which one would give a pH of greater than 7, and KF was one of the answer choices then the answer would have been KF:
KF + H2O -> HF + KOH (KOH is a strong base and HF is a weak acid, therefore the solution would be more basic)

Actually NaCO3 would be more basic too!

 

[iwannabadentist]

is it AlCl3 and FeCl3?

 

[PooyaH]

is it AlCl3 and FeCl3?

Yeah I didn't see the last one! FeCl3 would react the same way as AlCl3 would

 

[tizom]

its FeCl3 AlCl3 and NH4NO3

i didnt understand 🙁 it says NO3 is a spectator ion, and NH4+ + H20 -> NH3 + H3O+

 

[iwannabadentist]

i guess that makes sense...but i would never have been able to come up with that on my own :-\

 

[sweetcinuhstix]

its FeCl3 AlCl3 and NH4NO3

i didnt understand 🙁 it says NO3 is a spectator ion, and NH4+ + H20 -> NH3 + H3O+

FeCl3
Fe=lead=precipitate
Cl3+H20=HCL! strong acid!

Al=aluminum=precipitate
Cl3+H20=HCL! strong acid!

NH4NO3
NH4=like you said
NO3=spectator ions, also include sulfate, perchlorate.
Spectator ions appear on both sides of the <-->.