If each of the salts listed in A through E were dissolved in water to make a 0.1 M solution, which solution would have the lowest pH?

a. NaNO2
b. NaF
c. AlCl3
d. KNO3
e. Na3PO4

1 answer

The lowest pH means the strongest acid.
I do these this way but your teacher may want another method. I hydrolyze each salt.
NaNO2 + HOH ==> HNO2 + NaOH
HNO2 is a weak acid, NaoH a strong base, the solution will be basic.
NaF + HOH ==> HF + NaOH
HF is a weak acid, NaOH is a strong base, the solution will be basic.
Etc.Find the one that is acidic. In case more than one is acidic, the strongest acid will be the one you want.