AQA A2 Chemistry C23 Transition Metal Kerboodle Answers.

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C23.1 The general properties of transition metals AQA A2 Chemsitry C23 Transition Metals Kerboodle Answers: Page No. 105

1 a a Mn²⁺ ion 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ b a Mn³⁺ ion 1s²2s²2p⁶ 3s² 3p⁶ 3d⁴ 2 a 1s²2s² 2p⁶ 3s² 3p⁶ b The two 4s electrons c One of the 3d electrons

23.2 Complex formation and the shape of complex ions AQA A2 Chemsitry C23 Transition Metals Kerboodle Answers : Page No. 109

1 a i [Cu(H₂O)₆]²⁺ Octahedral ii [Cu(NH₃)₆]²⁺ Octahedral iii [CuCl₄ ]^2- Tetrahedral b  6,6,4 c Cl^– is a larger ligand than either ammonia or water, so fewer ligands can fit around the metal ion. 2. a The rwo negatively charged oxygen atoms. because they have lone pairs of electrons.

c Bidentate

23.3 Coloured ions AQA A2 Chemsitry C23 Transition Metals Kerboodle Answers : Page No. 112

1 a The copper ion has part-filled ct-orbitals, so electrons can move from one d-orbital to another and absorb light. Zinc has full d-orbitals. b Blue c They are absorbed. 2 a Which mixture absorbs most light? 5:5 b 5:5 c [NiEDTA]^2-

23.4 Variable oxidation states of transition elements AQA A2 Chemsitry C23 Transition Metals Kerboodle Answers : Page No. 118

1 a b This low oxidation state can be oxidised by air. 2 0.0698 g 3 Ee- for the reaction: Cl₂(g) + 2e- → 2cl^– is + 1.36 V, but Ee-for the reaction of Cr20 7 and c1-and is 0.03 V. Therefore the reaction is not feasible. Hence potassium dichromate(VI) will nor oxidise chloride ions ro chlorine.

23.5 Catalysis AQA A2 Chemsitry C23 Transition Metals Kerboodle Answers : Page No. 122

1 a Homogeneous catalysts are in the same phase as the reactants, heterogeneous catalysts are in a different phase from the reactants. b i Heterogeneous ii Heterogeneous iii Homogeneous 2 It lowers the activation t.!nergy. This means that reactions can be carried out at a lower temperature than without tht.! catalyst, so saving energy and money. 3 First. iron(III) oxidises iodide ro iodine, itself being reduced to iron(ll): 2Fe³+(aq) + 21-(aq) _, 2Pe²+(aq) + 1(aq) 2 Then the peroxodisulfate ions oxidise rhe iron(II) back to iron(Ill): S₂0/-(aq) + 2Fe²+(aq) _, 2SO/-(aq) + 2Fe³+(aq) Catalyst is needed since the reaction is slow. The reaction is slow since both reactants are negative ions. These ions will repel each other, reducing the chance of effective collisions. 4 5Mn3•(aq) + 4H₂0(1) 2Mn³•(aq) + c₂o/-(aq) —. 2C0₂(g) + 2Mn²+(aq) 4Mn²+(aq) + Mn0-(aq) + 8W(aq) -+ Banner 2

Practice questions: Page No. 123

1 (a) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ d-sub-shell / shell / orbitals / sub-level full (or not partially full) (b Atom or ion or transition metal bonded to / surrounded by one or more ligands by co–ordinate / dative (covalent) bonds / donation of an electron pair (c) H₂ / hydrogen No lone / spare / non-bonded pair of electrons (d) (i)

+2 OR 2+ OR Pd2+

(ii) Tetrahedral

• Square planar

2 (a) (ll) ions are blue. (i) Absorbs (certain frequencies of) (white) light / photons

• D-electrons excited / promoted
• The colour observed is the light not absorbed / light reflected / light transmitted

(ii) E is the energy gained by the (excited) electrons (of Cu²⁺)

• h (Planck’s) constant
• ν frequency of light (absorbed by Cu²⁺ (aq))

(iii)

[Cu(H2O)6]2+ + 4Cl– → [CuCl4]2- + 6H2O Tetrahedral Cl– / Cl / chlorine too big (to fit more than 4 round Cu)

(b) Lone pair(s) on O^–/ O (c) (i) [Cu(H₂O)₆]²⁺ + 2C₂O₄^2- → [Cu(C₂O₄)2(H2O)₂]^2- + 4H₂O

• Product correct
• Equation balanced
• 6
• Octahedral

(ii) 90⁰ 3 (a) A ligand is a species which can donate a pair of electrons to a metal ion.

• A co-ordinate bond is a covalent bond in which both electrons are donated by one atom.

(b) (i) [Co(H₂O)₆]²⁺ + 4Cl^– → [CoCl₄]^2- + 6H₂O Pink                                blue (ii) [Co(NH₃)₆]²⁺ + 3NH₂CH₂CH₂NH₂ → [Co(NH₂CH₂CH₂NH₂)₃]²⁺ + 6NH₃

• More molecules and/or ions formed.
• Increase in entropy because the reaction involves an increase in the number of molecules and ions.

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