The species among the following,which can act as an acid and a base is

For the reaction $NH_4^+ + S^{2-} \rightleftharpoons NH_3 + HS^-$,identify the nature of $NH_3$ and $HS^-$ in the context of the Brønsted-Lowry theory.

Which type of reaction occurs between $H_{2}SO_{4}$ and $HNO_{3}$ in nitration?

Which of the following is a Lewis acid but not a Bronsted acid?

Four species are listed below:
$i. \, HCO_3^-$
$ii. \, H_3O^{+}$
$iii. \, HSO_4^-$
$iv. \, HSO_3F$
Which one of the following is the correct sequence of their acid strength?

The conjugate base of $HSO_3^-$ is ......