PROBLM Identify the major species in a 030 M HNO3 solution a

PROBLM Identify the major species in a 0.30 M HNO3 solution at 25°C, which is used for etching copper metal. (a) Calculate [H30+] and pH for the solution. (b) Calculate OH and pOH for the solution by using two alternative ways.

Solution

nitric acid HNO3 is a strong acid.

It dissocaites almost completely to give H3O+ and NO3- ions in solution.

HNO3 +H2O --------------> H3O+ + NO3-

Thus the major species in solution are H3O+ and NO3-

[acid] = 0.30M = [H3O+] for strong acids

pH of strong acid = -log [H3O+]   

= -log 0.30

=0.5228

b) calculation of pOH and [OH-]

method 1)

For any aqueous solution [H3O+][OH-] = Kw = 1.0x10^-14

Thus [OH-] in the solution = Kw/[H3O+]

= 3.33x10^-14 M

and pOH = -log[OH-]

= 13.4771

method 2)

we know pH + pOH of a solution = pKw =14

Thus pOH of HNO3 solution = 14 -0.5228

=13.4772

and [OH-] = antilog [-13.4772]

=3.33x10^-14