Which of the following can act both as Bronsted acid and Bronsted base?
`(i) HCO_(3)^(-) (ii) NH_(3) (iii) O^(2-) (iv) HCl`

Options

A. (i) and (ii)
B. (ii) and (iii)
C. None of the above
D. All of the above

Answer

A

Explanation

According to bronsted-lowry theory, acids are proton donors and bases are proton acceptors.
`(i) HCO_(3)^(-)-H^(+) rarr CO_(3)^(2-)`
`HCO_(3)^(-) + H^(+) rarr H_(2)CO_(3)`
(ii)`NH_(3)-H^(+) rarr NH_(2)^(-)`
`NH_(3) + H^(+) rarr NH_(4)^(+)`
(iii)`O^(2-) + H^(+) rarr HO^(-)`
(iv)`HCl-H^(+) rarr Cl^(-)`
Hence, `HCO_(3)^(-) and NH_(3)` can act as bronsted acids as well as bronsted base.