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(i) Hydrogen fluoride is a weaker acid than hydrogen chloride in aqueous solution. Or Which is a stronger acid in aqueous solution, HF or HCI ? (ii) In aqueous solution, HI is a stronger acid than HCI ? (iii) F atom is more electronegative than I atom, yet HF has lower acid strength than HI. Explain. |
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Answer» Solution :(i) 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-Cl bond. As a result, in aqueous solution, H-Cl bond can break more easilyto form `H^(+)` ion than H-F bond. Thus, HYDROGEN fluoride is a weaker ACID than hydrogen CHLORIDE in aqueous solution. (ii) Due to smaller size of Cl as compared to I, bond dissociation energy of H-Cl bond is much higher than that of H-I bond. As a result, in aqueous solution, H-I bond breaks more easily to release `H^(+)` ion than H-Cl bond. Thus, HI is a stronger acid than HCl in aqueous solution. (iii) F atom being smaller in size than I atom, the bond dissociation energy of H-F is very high as compared to that of H-I bond. Consequently, H-I bond breaks more easily to release `H^(+)` ion than H-F bond and thus HI is a stronger acid than HF. |
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