A Level Chemistry Transition Metals Reactions PDF

A LEVEL CHEMISTRY 3.2.5 TRANSITION METALS COPPER COMPLEXES [Cu(H2O)6]2+ [CuCl4]2- 2+...

A LEVEL CHEMISTRY 3.2.5 TRANSITION METALS COPPER COMPLEXES [Cu(H2O)6]2+ [CuCl4]2- 2+ 2- H2O Cl : : H2O : :OH2 + conc. HCl(aq) Cu + H2O(l) Cu L.S. Cl : : H2O: : OH2 Cl : H2O Cl : Blue Solution Yellow-Green Solution NOTE: Coordination number is 4, + NaOH(aq) not 6 here as the Cl- + excess NH3(aq) ligands are large & or charged. Fewer can fit A-B L.S. around the metal ion. + NH3(aq) drop by drop [Cu(H2O)4(OH)2] [Cu(NH3)4(H2O)2]2+ OH H2O 2+ : : H2O : :OH2 H3N : :NH3 + excess NH3(aq) Cu Cu L.S. : H2O: OH2 H3N: : NH3 : OH : H2O Blue Precipitate Deep Blue Solution A-B = Acid-base reaction L.S. = ligand substitution reaction AQA www.chemistrycoach.co.uk © scidekick ltd 2024 A LEVEL CHEMISTRY 3.2.5 TRANSITION METALS IRON II COMPLEXES [Fe(H2O)6]2+ 2+ H2O : H2O : :OH2 + conc. HCl(aq) No Further Change / Reaction Fe : H2O: OH2 : H2O Green Solution + NaOH(aq) or A-B + NH3(aq) drop by drop [Fe(H2O)4(OH)2] OH : H2O : :OH2 + excess NH3(aq) No Further Change / Fe Reaction : H2O: OH2 : OH Green Precipitate NOTE: This green precipitate may turn brown as some Fe2+ may be oxidised to Fe3+. A-B = Acid-base reaction L.S. = ligand substitution reaction AQA www.chemistrycoach.co.uk © scidekick ltd 2024 A LEVEL CHEMISTRY 3.2.5 TRANSITION METALS IRON III COMPLEXES [Fe(H2O)6]3+ [FeCl4]- 3+ - H2O Cl : : H2O : :OH2 + conc. HCl(aq) Fe + H2O(l) Fe Cl : : H2O: L.S. : OH2 Cl : H2O Cl : Purple Solution Yellow Solution NOTE: Coordination number is 4, + NaOH(aq) not 6 here as the Cl- ligands are large & or charged. Fewer can fit A-B around the metal ion. + NH3(aq) drop by drop [Fe(H2O)3(OH)3] OH : H2O : : OH + excess NH3(aq) No Further Change / Fe Reaction : H2O: OH2 : OH Brown Precipitate A-B = Acid-base reaction L.S. = ligand substitution reaction AQA www.chemistrycoach.co.uk © scidekick ltd 2024 A LEVEL CHEMISTRY 3.2.6 REACTIONS OF IONS IN SOLUTION METAL-AQUA IONS YOU NEED TO KNOW [Cu(H2O)6]2+ [Fe(H2O)6]2+ 2+ 2+ H2O H2O : : H2O : :OH2 H2O : :OH2 Cu Fe : : H2O: OH2 H2O: OH2 : H2O : H2O Blue Solution Green Solution [Fe(H2O)6]3+ [Al(H2O)6]3+ 3+ 3+ H2O H2O : : H2O : :OH2 H2O : :OH2 Fe Al : : H2O: OH2 H2O: OH2 : : H2O H2O Purple Solution Colourless Solution You need to know the reactions Testing for and observations of these ions Metal-Aqua Ions with: NaOH NH3 Na2CO3 Here’s the cheat sheet! AQA www.chemistrycoach.co.uk © scidekick ltd 2024 A LEVEL CHEMISTRY 3.2.6 REACTIONS OF IONS IN SOLUTION ACIDITY OF META-AQUA IONS Both 2+ and 3+ complex ions cause a solution to become acidic. However, 3+ complex ion solutions are more acidic than 2+. e.g. [Cu(H2O)6]2+ [Fe(H2O)6]3+ [Fe(H2O)6]2+ [Al(H2O)6]3+ pH 5-6 pH1-3 THE EXPLANATION H2O H The positive central ion attracts the : coordinately bonded electrons H2O : :O towards it, leaving oxygen short of H electrons. M This causes the O-H bond in a H2O : ligand to become polarised and the H2O: OH2 bond breaks. : H2O This releases a H+ into solution, increasing the [H+] and making it acidic. 3+ metal-aqua ions have a lower pH in solution as a greater number of H+ are released into solution. This is because a 3+ ion has a greater charge density than a 2+ ion, so is more effective at drawing electrons towards it, causing greater polarisation in the O-H bond, increasing the chances of a H+ being released. In both cases, only one H+ is released per complex. 2+ ions: [M(H2O)6]2+(aq) ⇌ [M(H2O)6]+(aq) + H+(aq) 3+ ions: [M(H2O)6]3+(aq) ⇌ [M(H2O)6]2+(aq) + H+(aq) Only a 3+ complex ion will react with Na2CO3 2M(H2O)6]3+(aq) + 3CO32-(aq) ⇌ 2[M(H2O)3(OH)3(s) + 3CO2(g) + 3H2O(l) Precipitate! Bubbles! AQA www.chemistrycoach.co.uk © scidekick ltd 2024 A LEVEL CHEMISTRY 3.2.6 REACTIONS OF IONS IN SOLUTION AMPHOTERIC METAL HYDROXIDES An amphoteric substance means that it can act as an acid or a base. Amphoteric metal hydroxides react with / dissolve in both acids and bases. e.g. aluminium hydroxide, Al(OH)3 [Al(H2O)3(OH)3] OH : Al(OH)3 actually exists as a H2O : : OH complex, [Al(H2O)3(OH)3](s) Al Essentially, it's just Al(OH)3 with 3 H2O ligands coordinately bonded. : H2O: OH2 Make sure you learn the equations : below… OH White Solid Reaction with Acids (HCl) [Al(H2O)3(OH)3](s) + 3HCl(aq)→ [Al(H2O)6]3+(aq) + 3Cl-(aq) white solid colourless solution The HCl donates protons to the 3 OH- ligands creating 3 more H2O ligands, creating a soluble [Al(H2O)3]3+(aq) octahedral complex. Reaction with Bases (NaOH) [Al(H2O)3(OH)3](s) + OH-(aq)→ [Al(OH)4]-(aq) + 3H2O(l) white solid colourless solution A ligand substitution reaction occurs. One OH- ion substitutes for 3 H2O ligands, creating a soluble [Al(OH)4]-(aq) tetrahedral complex. AQA www.chemistrycoach.co.uk © scidekick ltd 2024