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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 |
| " "Give the full electron configuration of the following atoms and ions. a V atom b V3+ ion | " "Give the full electron configuration of the following atoms and ions. a V atom 1s2 2s2 2p6 3s2 3p6 4s2 3d3 (1) b V3+ ion 1s2 2s2 2p6 3s2 3p6 3d2 |
| " " Explain why copper is classed as a transition metal. | " a common ion Cu2+ has incomplete d subshell |
| What is the shape of all 6 coordinate complex ions | octahedron |
| What are the two possible shapes of four coordinate complex ions. | square planar or tetrahedron. |
| "Give the full electron configuration of the following atoms and ions. a Cr atom b Cr3+ ion | " "a Cr atom 1s2 2s2 2p6 3s2 3p6 4s1 3d5 b Cr3+ ion 1s2 2s2 2p6 3s2 3p6 3d3 |
| " "The complex [Cu(H2O)6]2+ reacts irreversible with Na4EDTA. a Write an equation for the reaction. | " " [Cu(H2O)6]2+ + EDTA4– → [Cu(EDTA)]2– + 6H2O |
| " [Cu(H2O)6] 2+ + EDTA4– → [Cu(EDTA)]2– + 6H2O b Explain clearly why this reaction is irreversible. | for reverse reaction ∆H is negligible as same number of similar bonds are broken and formed for reverse reaction ∆S is very negative as go from 7 to 2 aqueous particles therefore ∆G for reverse reaction is very positive |
| "Give the full electron configuration of the following atoms and ions. a Co atom b Co3+ ion | " "Give the full electron configuration of the following atoms and ions. a Co atom 1s2 2s2 2p6 3s2 3p6 4s2 3d7 b Co3+ ion 1s2 2s2 2p6 3s2 3p6 3d6 |
| " "The complex [Pt(NH3)2Cl2] exists as two stereoisomers. a What are stereoisomers? | " same structural formula but different arrangement of atoms in space |
| "Draw the cis stereoisomer of [Pt(NH3)2Cl2] , name its shape, ligand-Pt-ligand bond angles, give its co-ordination number and oxidation state of the platinum. | " "Name of shape = square planar ligand-Pt-ligand bond angles = 90° Co-ordination number = 4 Oxidation state of Pt = +2 |
| " "A complex absorbs visible light at 582 nm. Calculate the energy gap between the d orbitals in J. [Planck’s constant is 6.63 x 10-34 Js and the velocity of light is 3.00 x 108 ms-1 ] | " 3.42 x 10–19 J |
| "What are concordant titres? | " "What are concordant titres? titres within 0.1 cm4 |
| " "During t titrations using KMnO4, all readings from the burette are taken from the top of the meniscus. Explain why. cannot see the bottom due to the dark colour | " cannot see the bottom due to the dark colour |
| In titrations using KMnO4 Why does it not matter that these readings were all taken from the top of the meniscus? | finding the difference in volume and so it is fine as we read it the same way each time |
| "What would have happened to the mean titre if the volumetric flask had been filled up so that the top (rather than the bottom) of the meniscus was on the line? Explain your answer. | " " solution would have been more concentrated than it should have been so titre would have been greater |
| Write an equation for this reaction and classify its type [Cu(H2O)6] 2+ → [Cu(H2O)4(OH)2] using NaOH | " [Cu(H2O)6] 2+ + 2OH– → [Cu(H2O)4(OH)2] + 2H2O reaction type hydrolysis |
| " Write an equation for this reaction and classify its type [Cu(H2O)6]2+ → [Cu(H2O)4(OH)2] using NH3 | "[Cu(H2O)6]2+ + 2NH3 → [Cu(H2O)4(OH)2] + 2NH4+ reaction type hydrolysis |
| " Write an equation for this reaction and classify its type [Cu(H2O)6]2+ → [CuCl4]2– using HCl | " [Cu(H2O)6]2+ + 4Cl– → [CuCl4]2– + 6H2O reaction type ligand substitution |
| " Write an equation for this reaction and classify its type [Cu(H2O)6] 2+ → [Cu(NH3)4(H2O)2]2+ using NH3 | " [Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O reaction type hydrolysis then ligand substitution |
| " Write an equation for this reaction and classify its type e [Cu(H2O)6]2+ → CuCO3 using Na2CO3 | "equation [Cu(H2O)6]2+ + CO32– → CuCO3 + 6H2O reaction type precipitation |
| " Write an equation for this reaction and classify its type [Cu(H2O)4(OH)2] → [Cu(NH3)4(H2O)2]2+ using NH3 | "equation [Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OH– reaction type ligand substitution |
| " "Give observations and equations for the following reactions Addition of sodium hydroxide solution drop-wise and to excess to a solution of iron(II) sulfate. | " "Dropwise green solution to green precipitate [Fe(H2O)6]2+ + 2OH– --> Fe(H2O)4(OH)2 + 2H2O excess: no further reaction over time, green precipitate becomes brown precipitate |
| " Give observations and equations for the following reactions Addition of ammonia solution drop-wise and to excess to a solution of copper(II) chloride | "dropwise: blue solution to blue precipitate [Cu(H2O)6]2+ + 2NH3 --> Cu(H2O)4(OH)2 + 2NH4+ excess: blue precipitate to deep blue solution Cu(H2O)4(OH)2 + 4NH3 --> [Cu(H2O)2(NH3)4]2+ + 2OH– + 2H2O |
| " Give observations and equations for the following reactions Addition of sodium carbonate solution drop-wise and to excess to a solution of aluminium sulfate. | "dropwise: colourless solution to white precipitate and gentle bubbles 2[Al(H2O)6]3+ + 3CO32– ---> 2Al(H2O)3(OH)3 + 3H2O + 3CO2 excess: no further reaction |
| " Why does the reaction between S2O82- ions and I- ions have a high EA in normal conditions? | Two negative ions are reacting. They repel each other so EA is high |
| "Define homogeneous catalyst | " " A catalyst that is in the same phase as the reactants |
| " How do heterogeneous catalysts work? | "Reactants adsorb to the catalyst’s surface at active sites. This weakens bonds within the reactants, holds reactants close together on the surface and/or in the correct orientation to react. products desorb from the active site |
| " What happens to Co2+, Cu2+ and Fe3+ ‘s coordination numbers when Cl- ligands replace NH3or H2O ligands? | Decreases from 6 to 4 as Cl- is a much larger ligand than H2O and NH3 |
| "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+ |
| "Name this complex ion [Cu(CN)6]4- | Hexacyanocuprate(II) |
| "Name this complex ion [Cr(H20)6]3+ | hexaaquachromium(III) ion |
| 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 |
| " """Name this complex ion [Co(H2O)4Cl2]+ | " "Tetraaquadichlorocabalt(III) |
| " Define bidentate ligand | "A ligand which can donate two lone pairs of electrons from two different atoms to form two coordinate bonds with the central metal ion |
| " 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 |
| " |
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davenantchemistry
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