Which of the following pairs cannot exist together in a solution?

Heating iron sulfide produces sulfur oxide,which reacts with water to form an acid. What is the basicity of this acid?

The conjugate base of $HSO_4^-$ is:

The dissociation constants of two acids $HY$ and $HZ$ are $2.88 \times 10^{-4}$ and $1.8 \times 10^{-5}$ respectively. The relative strength of the acids will be :-

Non-metallic oxides dissolve in water to form

For the species $HSO_4^{-}$ and $NH_3$,their conjugate acids respectively are