(a) What are conjugate bases of each of the following :
`HS^(-), H_3O^(+), H_2PO_4^(-), HSO_4^(-), CH_3COOH, [Al(H_2O)_6]^(3+), H_2SO_4`
(b) Give the conjugate acids of the following :
`OH^(-), HCO_3^(-), HPO_4^(2-), CH_3NH_2, CO_3^(2-), CH_3COOH, NH_2^(-), HCOO^-`
(c ) Which of the following behave both as Bronsted acids as well as Bronsted bases ?
`H_2O, HCO_3^(-), H_2SO_4 , H_3PO_4 , HS^-`

Explanation

(a)Conjugate base :
`HS^(-) : S^(2-)`
`H_3O^(+) : H_2O`
`H_2PO_4^(-) : HPO_4^(2-)`
`HSO_4^(-) : SO_4^(2-)`
`CH_3COOH:CH_3COO^-`
`[Al(H_2O)_6]^(3+) : [Al(H_2O)_5OH]^(2+)`
`H_2SO_4 : HSO_4^-`
(b)Conjugate acids :
`OH^(-) : H_2O`
`HCO_3^(-) : H_2CO_3`
`HPO_4^(2-) : H_2PO_4^(-)`
`CH_3NH_2 : CH_3NH_3^+`
`CO_3^(2-) : HCO_3^(-)`
`CH_3COOH : CH_3COOH_2^+`
`NH_2^(-) : NH_3`
`HCOO^(-) : HCOOH`
(c) `H_2O , HCO_3^(-) ,HS^-` behave both as acids and bases. These are called amphoteric substances.