determine the relative Brønsted-Lowry base strengths from strongest to weakest?

Question

HNO3 + H2O ----->H3O+ + NO3-
HF + H2O -------> H3O+ + F-
<---------

F-
H2O
H3O+
HNO3
NO3-

Answer 1

F- > H2O > NO3- > HF > H3O+ > HNO3

HF + H2O is a reversible reaction, suggesting HF is a weaker acid than HNO3. The fact that it is a reversible reaction suggest that H3O+ is of comparable acidity as HF, in fact judging from the pKa values of H3O+ and HF, we see that H3O+ is a stronger acid than HF. [ base strength: HF > H3O+ > HNO3]

The corrsponding base of a strong acid is a weak base. [base strength: F- > H2O > NO3-]

Answer 2

H2O > F- > NO3- > HF > HNO3 > H3O+