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Explain acid-base and its type according (A) Arrhenius and (B) Bronsted-Lowry by examples. |
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Answer» SOLUTION :(A) According to Arrhenius acid-base: As per this law strength is determine by ionization. "The acid or base which undergo complete ionization in its AQUEOUS solution is called strong acid or strong base." Strong Acids : Perchloric acid `(HClO_4)`,Hydrochloric acid (HCI), Hydrobromic acid (HBr), Hydroiodic acid (HI), Nitric acid (`HNO_3`), Sulphuric acid (`H_2SO_4`) are termed strong acid. Its are acting of proton donor and almost not present as a atom in solution. Strong Bases : Lithium hydroxide (LiOH), Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Caesium hydroxide (CsOH), Barium hydroxide `(BA(OH)_2)` are strong base according to Arrhenius. These bases are almost not present as a non ionised atom in aqueous solution. Weak Acid-Base : According to Arrhenius its ionization is much LESS in aqueous solution. This type of acid-base remain as an unionized molecule in solution. e.g. `Mg(OH)_2`, `Ca(OH)_2`, are weak base and HCN, `H_2S, H_3PO_4`,.... are weak acid. (B) According to Bronsted-Lowry Acid and Base : According to Bronsted-Lowry concept of acids and bases, where in a strong acid means a good proton donor and a strong base means a good proton acceptor. Strong Acid : Strong acid donate proton to strong base. The complete dissociation of strong acid in to water. So, conjugate base of strong acid is more weak. Perchloric acid `(HClO_4)`, Hydrochloric acid (HCI), Hydrobromic acid (HBr), Hydroiodic acid (HI), Nitric acid `(HNO_3)`, Sulphuric acid `(H_2SO_4)` are strong acids because they are good proton donor. Its conjugate base `ClO_4^(-) , Cl^(-) , Br^(-), I^(-), NO_3^(-), HSO_4^(-)`are much weak bases respectively. They are much weak bases than water. Strong Base: NaOH, KOH, LIOH, CsOH, `Ba(OH)_2` are good proton acceptor, so they are strong bases. They from completely `OH^-` in solution. These strong bases give conjugate acid in solution. Weak Acid : According to Bronsted, weak acids are weak proton donor and partially dissociated in aqueous medium and thus the solution mainly contains undissociated HA molecules. Weak acid are `HNO_2, HF, CH_3COOH`. Its conjugate base `NO_2^(-), F^(-) , CH_3COO^-` are very strong bases. These conjugate bases are good proton acceptor. They are much proton acceptor them `H_2O`. So, strong bases than water. Certain water SOLUBLE organic compounds like phenolphthalein and bromothymol blue behave as weak acids and exhibit different colour in their acid (HIn) and conjugate base `(In^-)` forms. `{:(HIn_((aq))+H_2O_((l)) hArr, H_3O_((aq))^(+)+, In_((aq))^(-)),("acid indicatorcolour A", "conjugate acid colour-B","conjugate base") :}` Such compounds are useful as indicators in acid-base titration and finding out `H^+` ion concentration. |
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