TEACH ME how to do question 2 through your explanations.

Answer:
Explanation:
The first two are easy:
H2O, H3O+ and OH- all exist in an equilibrium
[H3O+] = [OH-] = 10^-7 M
HCl is a strong acid so 1M of it will disassociate completely
[H3O+] = [Cl-] = 1 M
The third one is also an equilibrium as HNO2 is a weak acid. Ka is given so [HNO2] and [NO2-] can be calculated.
The fourth one is a buffer solution so its pH can be looked up to give the concentrations.
Answer:
Explanation:
H20 has pH of 7
1st reaction [H30+] = 10^-7M
[OH-] = 10^-7M
1M HCl has pH of 0
2nd reaction [H3O+] = 1M
[Cl-] = 1M
given Ka = 4.6x10^-3 = [H3O+]x[NO2-] / [HNO2]
and [HNO2] + [NO2-] = 1M
each concentration can be solved
beaker D is a buffer solution n requires more info 2 solve