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Transition metals
AQA A Level Chemistry
| Question | Answer |
|---|---|
| In general, what is a d-block element? | An element whose outermost electron is in a d orbital |
| In general, what is a ligand substitution reaction? | A reaction in which one or more ligands is/are replaced by one or more different ligands in a complex |
| In general, what is a transition element? | An element which has at least one stable ion with a partially filled d-orbital |
| List the four typical properties of a transition metal | "Variable oxidation states The formation of coloured aqueous ions. The formation of complex ions Their use as Heterogeneous Catalysts |
| What is the electronic structure of copper? | "1s2 2s2 2p6 3s2 3p6 4s1 3d10 |
| Why is zinc not a transition metal? | It does not form a stable ion which has unfilled d orbitals |
| Explain in terms of ionisation energy why Transition metals have a variety of oxidation states | "Transition metals have a large number of oxidation states because when removing d electrons there is never a big jump from one ionisation energy to the next. |
| List the five colours of the five oxidation states of vanadium | " yellow VO2+, blue VO2+ ions, green V3+ ions, V2+ |
| Define bidentate ligand | A ligand which can donate two lone pairs of electrons to form two coordinate bonds with the central metal ion |
| Define complex | A central metal ion surrounded by ligands |
| Define coordinate (dative covalent) bond. | An electrostatic force of attraction between the shared pair of electrons and the nuclei of the atoms involved where both electrons are from the same atom. |
| Define coordination number. | the number of dative covalent bonds formed to a central metal ion in a complex |
| Define ligand. | A molecule or ion which can donate one or more lone pairs of electrons to form coordinate (date covalent) bond(s) with a central metal ion in a complex |
| Define monodentate ligand. | A ligand which can donate one lone pair of electrons to form one coordinate bond with the central metal ion |
| Define multidentate ligand | A ligand which can donate multiple lone pairs of electrons to form multiple coordinate bonds with the central metal ion |
| Describe the chelate effect and how it affects the stability of ligands | "When we replace ligands with those that form more co-ordinate bonds, reaction is feasible (driven by increase in entropy)Reverse reaction is NOT feasible due to large +ve ΔG caused by big decrease in entropy |
| "Name this complex ion [Cr(H20)6]3+ | hexaaquachromium(III) ion |
| "Name this complex ion [Cu(CN)6]4- | Hexacyanocuprate(II) |
| "Name this complex ion [Co(H2O)4Cl2]+ | Tetraaquadichlorocabalt(III) |
| Write an equations for the reaction of chloride ions with Hexaaquacopper(II) | [Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O |
| Write an equation for the reaction of excess aqueous ammonia with hexaaqucopper(II) ions | [Cu(H2O)6]2+ + 2NH3 → [Cu(H2O)4(OH)2] + 2NH4+ (hydrolysis) |
| Write an equations for the reaction of a few drops of aqueous ammonia with hexaaqucopper(II) ions | [Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O |
| What are the two possible shapes for complex ions with a coordination number of 4 | Tetrahedral and square planar |
| Explain the origin of the colour of transition metal aqua ions such as [Cr(H2O)6]3+. | "d – orbitals/subshell/energy level split (in energy by (ligands), Electron transitions/jumps from lower to higher energy level, Absorbs light in visible region/reference to white light |
| Explain why [Zn(H2O)6]2+ ions have no colour | " d-(sub) shell / orbitals are full / 3d10 arrangement of electrons (1), No jumps of d-electrons /no d-d transitions |
| How does a catalyst work? | "substance that speeds up reaction without being used up, They provide an alternative mechanism with lower activation energy. |
| Define a heterogenenous catalyst | "Heterogeneous catalyst is in different phase to the reactants. |
| Define a homogenenous catalyst | Homogeneous catalyst is in the same phase as the reactants. |
| Describe the three stages of a heterogeneneous catalyst work? | Reactants adsorbed onto surface (onto active sites), Reaction takes place, Products are desorbed (leave the surface). |
| Write two equations that show the action of Fe2+ as a homoegeneous catalyst for this reaction 2 I- + S2O82- -------> I2 + 2 SO42- | "2 Fe2+ + S2O82- → 2 Fe3+ + 2 SO42- , 2 Fe3+ + 2 I- → 2 Fe2+ + I2 |
Created by:
JBearfield
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