Question

Consider the following data on some weak acids and weak bases:

acid Ka name formula hypochlorous acid HClO ×3.010−8 hydrofluoric acid HF ×6.810−4

base Kb name formula pyridine C5H5N ×1.710−9 ammonia NH3 ×1.810−5

Use this data to rank the following solutions in order of increasing pH. In other words, select a '1' next to the solution that will have the lowest pH, a '2' next to the solution that will have the next lowest pH, and so on.

solution	Ph
0.1 M C5H5NHCl	?
0.1 M NH4Br	?
0.1 M KClO	?
0.1 M NaI	?

Answer 1

C5H5NHCl is conjugate acid of C5H5NH2

So, its pH would be less than 7

NH4Br is conjugate acid of NH3

So, its pH would be less than 7

KClO is conjugate base of HClO

So, its pH would be more than 7

NaI is neutral salt.

So, its pH would be 7

C5H5NHCl is stronger acid as compared to NH4Br because Kb of NH3 is more.

So, pH of C5H5NHCl will be less than pH of NH4Br

Answer:

C5H5NHCl: 1

NH4Br: 2

KClO: 4

NaI: 3