In a 1.0× 10–6 m solution of ba(oh)2(aq) at 25 °c, identify the relative molar amounts of these species.

Thank you for posting your question here. Below is the solution:

HNO3 --> H+ + NO3- 
HNO3 = strong acid so 100% dissociation 
** one doesn't need to find the molarity of water since it is the solvent 

0M HNO3 
1x10^-6M H3O+ 
1x10^-6M NO3- 
1x10^-8M OH-the Kw = 1x10^-14 = [H+][OH-] 
you have 1x10^-6M H+ so, 1x10^-14 / 1x10^-6 = 1x10^-8M OH- 

1x10^-6 Ba(OH)2 = strong base, 100% dissociation 
1x10^-6M Ba2+ 
2x10^-6M OH- since there are 2 OH- / 1 Ba2+ 
0M Ba(OH)2 
5x10^-9M H3O+

The answer to the question is d

Fine out your self ponk