Question

Calssify the following as acid or base according to Bronsted-Lowry theory and name their corresponding conjugate base or acid
`(i) NH_(3) " " (ii) CH_(3)CO O^(-)`
`(iii) H_(3)O^(+) " " (iv) H^(-) " "(v) HO O^(-) " " (vi) S_(2)O_(8)^(2-)`.

Answer 1

According to Bronsted-Lowry theory, an acid is a substance which can donate a proton while base is a substance which can accept a proton.
(i) `NH_(3)` is a Bronsted base because it can accept a proton. Its conjugate acid is `NH_(4)^(+)`.
`NH_(3)` is also a Bronsted acid because it can donate a proton. Its conjugate base in `NH_(2)^(-)`.
(ii) `CH_(3)CO O^(-)` is a Bronsted base `(CH_(3)CO O^(-) + H^(+) rarr CH_(3)CO OH)`. Its conjugate acid is `CH_(3)CO OH`.
(iii) `H_(3)O^(+)` is a Bronsted acid `(H_(3)O^(+) rarr H_(2)O+H^(+))`. Its conjugate base is `H_(2)O`.
(iv) `H^(-)` is a Bronsted base `(H^(_)+H^(+) rarr H_(2) "in the reaction" H^(-) + H_(2)O hArr H_(2)+OH^(-))`. Its conjugate acid is `H_(2)`.
(V) `HO O^(-)` is a Bronsted acid (`HO O^(-) rarr O_(2)^(2-) + H^(+) ` in the reaction `H O O^(-) + H_(2)O rarr O_(2)^(2-) + H_(3)O^(+)`). Its conjugate acid is `O_(2)^(2-)` (peroxide ion).
(vi) `S_(2)O_(8)^(2-) ` is a Bronsted base `(S_(2)O_(8)^(2-) + 2 H^(+) rarr 2 HSO_(4)^(-) " in the reaction" S_(2)O_(8)^(2-) + 2 H_(2)O hArr 2 HSO_(4)^(-) + OH^(-))`. Its conjugate acid is `HSO_(4)^(-)`.