Answer:
Step-by-step explanation:
''A conjugate acid is formed when a proton is added to a base, and a conjugate base is formed when a proton is removed from an acid.''
In a conjugate acid-base pair, only difference between molecules is the amount of ''H''
One molecule must have 1 more H
in the last example HNO2 and H2O, difference is not only the H amount also H2O doesn't have N. So we can't say they are conjugate acid-base pair.