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Assign appropriate reasons for each of the following statements. (i)More metal fluorides are ionic in nature than metal chlorides. (ii) Hydrogen fluoride is a weaker acid than hydrogen chloride in aqueous solution. (iii)In aqueous solution HI is a stronger acid than HCI ? (iv) Addition of Cl_(2) to KI solution gives it a brown colour but excess of Cl_(2) turns it colourless. (v) Perchloric acid is a stronger acid than sulphuric acid. |
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Answer» (ii)Because of smaller size of `F` as compared to `Cl`, the bond dissociation energy of `H-F` bond is MUCH higher than that of `H-CI` bond.As a result, in aqueous solution, `H-Cl`, the bond can break more easily to form `H^(+)` ion than `H-F` bond.Thus, hydrogen fluoride is a weaker acid than hydrogen chloride in aqueous solution. (iii)Due to smaller size of `Cl` as compared to `l`, bond dissociation energy of `H-Cl` bond is much higher than that of `H-l` bond.As a result, in aqueous solution `H-i` bond breaks more easily to release `H^(+)` ion than `H-Cl` bond.Thus, `Hl` is a stronger acid than `HCl` in aqueous solution. (iv)`Cl_(2)` being a stronger oxidising agent than `l_(2)`, first oxidises `Kl` to give `l_(2)` which imparts brown colour to the solution. `2Kl (aq)+ Cl_(2) (g)to2 KCl (aq) + underset("Brown")(l_(2) (s))` If, however, `Cl_(2)` is passed in excess, the `l_(2)` thus formed gets further oxidized to iodic acid `(HIO_(3))` which is colourless. `5 Cl_(2) + l_(2) + 6 H_(2)Oto10 HCl +2 underset("Colourless")(HIO_(3))` (v)The oxidation state of `Cl` in PERCHLORIC acid is `+7` while that of `S` in sulphuric acid is `+6` `(##RES_INO_CHM_XII_V02_C03_E01_020_A01##)` Due to higher oxidation state and higher electronegativity of `CI, CIO_(3)` part of `HCIO_(4)` pullls the electrons of the `O-H` bond more strongly and hence can break the `O-H` bond more easily to liberate a proton than `SO_(2)` part in `H_(2)SO_(4)`.Thus, perchloric acid is stronger acid than sulphuric acid. |
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