Periodic Table Consolidation
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explain how chlorides of aluminium, silicon, and phosphorus exhibit acidic properties when dissolved in water IMPTTT
AlCl 3 (s) + 6 H2O (l) → [Al(H2O)6] 3+ (aq) + Cl– (aq) [Al(H2O)6] 3+ (aq) + H2O (l) ⇌ [Al(H2O)5 (OH– )] 2+ (aq) + H3O+ (aq) AlCl3 reacts with water to form hydrated ions. Since Al 3+ ions have a high charge density, it has a high polarising power to polarise electron cloud of water molecules, weakening the O – H bond, producing H3O+ ions in water via partial hydrolysis to form an acidic solution of pH 3. For SiCl 4 and PCl5 , SiCl 4 (l) + 2H2O(l) → SiO 2 (s) + 4HCl(aq) PCl 5 (s) + 4H2O(l) → H3 PO4 (aq) + 5HCl(aq) Both chlorides hydrolyse completely in water due to energetically accessible vacant 3d orbitals which can accommodate lone pairs of e- from water to form very acidic solutions of pH 2.
why does NaCl form a neutral solution (pH7) in water?
Na+ has a low charge density and low polarising power, does not undergo hydrolysis in water charge density: charge/radius
describe Na2O, MgO, Al2O3, SiO2, P4O10, SO3 oxides with water all oxides mentioned here are SOLID except SO3 (LIQUID) !
Na2O: forms 2NaOH MgO: forms Mg(OH)2 which forms Mg(OH)2 (aq) Al2O3 and SiO2: does not dissolve in water P4O10: forms 4H3PO4 SO3: forms H2SO4 for reactions to find MgO, react oxides with acid/base instead as MgO only slightly soluble in water, does not react readily
describe Na2O, MgO, Al2O3, SiO2, P4O10, SO3 oxides with acid/base all oxides mentioned here are SOLID except SO3 (LIQUID) !
• both Na2O & MgO basic oxides, only rxt with HCl to give respective chloride and water • Al2O3 amphoteric oxide, rxt with both acid and base, forms repective chloride & water with HCl, and 2Na+[Al(OH)4]- (aq) with NaOH and water • rest of the oxides are acidic, rxts with NaOH to give: Na2SiO3 (aq), 4Na3PO4 (aq), Na2SO4 (aq) and water (for all) as byproduct