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Discuss the Lowery - Bronsted concept of acids and bases. |
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Answer» Solution :Lowry - Bronsted Theory (Proton Theory) : According to Lowry - Bronsted concept , an acid is defined asa substance that has a tendency to donate a proton to another substance and base is a substance that has a tendency to accept a proton form other substance. In other WORDS, an acid is a proton donor and a base is a proton acceptor. When hydrogen chloride is dissolved in water, it donates a proton to the later. Thus, HCI BEHAVES as an acid and `H_2 O` is base. The proton transfer from the acid to base can be represented as `HCI+H_2 O hArr H_2 O^+ CI^-` When ammonia is dissolved in water, it accepts a proton from water. In this case, ammonia `(NH_3)` acts as a base and `H_2 O` is acid. The reaction is represented as `H_2 O+NH_3 hArr NH_4^(+)+OH^-` Let us consider the REVERSE reaction in the following equilibrium `underset(underset(("acid"))("Proton donar"))(HCI)+underset(underset(("base"))("Proton acceptor"))(H_2O)underset(underset(("acid"))("Proton donar"))( hArrH_3O^+)+underset(underset(("base"))("Proton acceptor"))(CI^-)` `H_3O^+` donates a proton to `CI^-` to form `HCI` i.e., the products also behave as acid base. In general, Lowry - Bronsted (acid - base) reactionis represented as `"Acid"_1+"Base"_2 hArr "Acid"_2+"Base"_1` The SPECIES that remains after the donation of a proton is a base `("Base"_1)` and is called the conjugate base of the Bronsted acid `("Acid"_2)`. In other words, chemical species that DIFFER only by a proton are called conjugate acid - base pairs. |
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