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Flashcards

Transition Metals

Kayla Price Chemistry AS - Level English 5.0Average rating 5.0 out of 5 (1 rating) 83 cards

Transition Metals

Cards in this deck (83)

  1. 1Where are transition metals found on the periodic table?d-block
  2. 2What is a transition metal?A d-block element that can form one or more stable ions with incompletely filled d-orbitals
  3. 3How many electrons can a d subshell hold?10 (has 5 orbitals)
  4. 4How are chromium d-orbitals filled and why?One electron in each orbital (4s1 3d5) as this is more stable than filling the 4s orbital.
  5. 5Why are 4s orbitals filled before 3d orbitals?They are at a lower energy level
  6. 6How are copper d-orbitals filled and why?4s1 3d10 because this is more stable so a 4s electron is promoted to a higher energy orbital.
  7. 7Why are scandium and zinc not transition metals?Scandium only forms one ion, Sc3+, which has an empty d-subshell and zinc only forms one ion, Zn2+, which has a full d-subshell.
  8. 8List all the stable ions that Vanadium can formVanadium(II) V^2+, Vanadium(III) V^3+, Vanadyl(IV) VO^2+, Vanadate(V) VO2+
  9. 9What makes an ion likely to form a compound or complex?The energy given out when the compound or complex forms is greater than the ionisation energy for the ion
  10. 10Describe the pattern for the successive ionisation energies for a transition metal4s and 3d orbitals are all at similar energy levels, so it takes a similar amount of energy to remove an electron from them. The is a large increase when all the 3d subshells are removed as there is there is a decrease in shielding
  11. 11Describe the pattern of successive ionisation energies for ChromiumLarge increase for second ionisation energy as electron is being removed from a half filled 3d subshell so it is very stable, then smaller increases as repulsion decreases
  12. 12What is a complex ion?a metal ion surrounded by dative covalently bonded ligands
  13. 13What is a ligand?an atom, ion or molecule that donates a pair of electrons to a central metal atom or ion
  14. 14What is a monodentate ligand? Give examplesA ligand with one lone pair (H20, NH3, Cl-, OH-)
  15. 15What is a bidentate ligand? Give examplesA ligand with two lone pairs of electrons (1,2-diaminoethane)
  16. 16What is a multidentate ligand?One with more than two lone pairs of electrons (EDTA4+)
  17. 17How would you calculate the oxidation number of a central metal ion in a complex?Total oxidation number (the overall charge of a complex ion is its oxidation number) - sum of charges of ligands
  18. 18What is the coordination number?Number of dative covalent (coordinate) bonds formed with the central metal ion
  19. 19What are the most common coordination numbers?6(smaller ligands) and 4(larger ligands)
  20. 20What is the shape of a six-fold coordination complex ion?octahedral (bond angles 90)
  21. 21What is the shape of a four-fold coordination complex ion?tetrahedral (bond angles 109.5)
    occasionally square planar shape
  22. 22How do transition metals form coloured complexes?When ligands bond to the transition metal ions the 3d orbitals split into two different energy levels. Electrons therefore require energy to jump to higher orbitals (excited states), which they get from visible light). The frequencies of light that aren's absorbed are transmitted as colour.
  23. 23Ti^3+Purple
  24. 24Ti^2+Violet
  25. 25VO2+Yellow
  26. 26VO^2+Blue
  27. 27V3+Green
  28. 28V2+Violet
  29. 29Cr2O7^2-Orange
  30. 30Cr3+Green
  31. 31MnO4^-Purple
  32. 32MnO4^2-Green
  33. 33Mn2+Pale pink
  34. 34Fe2+Pale green
  35. 35Ni2+Green
  36. 36Fe3+Yellow
  37. 37Co2+Pink
  38. 38Cu2+Pale blue
  39. 39Give the reduction half equation for VO2^+ and the oxidation states of vanadiumVO2^+ + 2H+ + e- <--> VO^2+ + H2O
    VO2^+ = +5
    VO^2+ = +4
  40. 40Give the reduction half equation for VO^2+ and the oxidation numbers of vanadiumVO^2+ + 2H+ +e- <--> V^3+ + H2O
    VO^2+ = +4
    V^3+ = +3
  41. 41Give the reduction half equation for V3+ and the oxidation numbers for vanadiumV3+ + e- <--> V2+
    V3+ = +3
    V2+ = +2
  42. 42Give the reduction half equation for V2+ and the oxidation numbers for vanadiumV2+ +e- <--> V
    V2+ = +2
    V = 0
  43. 43Which oxidation state of vanadium has the most positive electrode potential?+5
  44. 44Which oxidation state of vanadium has the highest reducing power?+2 because it has the most negative electrode potential, so is most likely to oxidise and produce electrons that go on to reduce another species
  45. 45List the chromium oxidation states in order of stabilityMost stable +3, +6, +2 Least stable
  46. 46What are the 2 ions chromium form with oxygen? What makes them good oxidising agents?Chromate(VI) ions CrO4^2- and dichromate(VI) ions Cr2O7^2-
    Easily reduced to Cr3+ because it is very stable
  47. 47What is the colour of aqueous Cr3+ ions?Violet but the water ligands are usually substituted by impurities so appears green
  48. 48What is the colour of aqueous dichromate ions?Orange
  49. 49What is the colour of aqueous chromate ions?Yellow
  50. 50What is the colour of aqueous Cr2+ ions?Blue
  51. 51How would you reduce dichromate ions? Give the equationAdd zinc and dilute acid:
    Cr2O7^2-(aq) + 14H+(aq) + 3Zn(s) --> 3Zn2+(aq) + 2Cr3+(aq) + 7H2O(l)
  52. 52How would you reduce Cr3+ ions? Give the equationAdd zinc in an inert atmosphere (Cr2+ ions very unstable so oxidises in the air)
    2Cr3+(aq) +Zn(s) --> Zn2+(aq) + 2Cr2+(aq)
  53. 53How would you oxidise Cr3+ ions? Give the equationAdd hydrogen peroxide in alkaline solution:
    2Cr3+(aq) + 10OH-(aq) + 3H2O2(aq) --> 2CrO4^2-(aq) + 8H2O(l)
  54. 54How would you create an equilibrium between chromate ions and dichromate ions? Give the equationAdd acid:
    2CrO4^2-(aq)+ 2H+(aq) --> Cr2O7^2-(aq) + H2O(l)
  55. 55How is chromium hydroxide made? Give the equationsBy reacting Cr3+ (green solution) with aqueous sodium hydroxide or aqueous ammonia which forms a chromium hydroxide precipitate (grey-green).
    [Cr(H2O)6]3+(aq) + 3OH-(aq) --> [Cr(OH)3(H2O)3](s) + 3H2O(l)
    [Cr(H2O)6]3+(aq) + 3NH3(aq) --> [Cr(OH)3(H2O)3](s) + 3NH4+(aq)
  56. 56Give equations to show the amphoteric characteristic of chromium hydroxideWhen acid is added the OH-
    ligands protonate forming a green solution of [Cr(H2O)6]3+:
    [Cr(OH)3(H2O)3](s) + 3H+(aq) --> [Cr(H2O)6]3+(aq)
    When excess alkali is added the H2O ligands deprotonate, forming a solution of [Cr(OH)6]3-:
    [Cr(OH)3(H2O)3](s) + 3OH-(aq) --> [Cr(OH)6]3-(aq) +3H2O(l)
  57. 57What is the difference between a ligand exchange reaction and an acid-base reaction?In ligand exchange reactions the whole ligand is swapped for a different type of ligand, whereas in acid base reactions the ligands are chemically modified by the addition or removal of H+
  58. 58Write the equation for adding excess ammonia to chromium hydroxide, name the type of reaction and give the colour change[Cr(OH)3(H2O)3](s) + 6NH3(aq) --> [Cr(NH3)6]3+(aq) + 3OH-(aq) + 3H2O(l)
    Grey green to purple
  59. 59Describe the process of forming chromium(II) ethanoate [Cr2(CH3COO)4(H2O)2](s)Sodium dichromate(VI) is reduced using zinc in acid to form a green solution of Cr3+ ions and then further reduced by the zinc to form a blue solution of Cr2+ ions.
    Sodium ethanoate is mixed with the Cr2+ solution and a red precipitate of chromium ethanoate forms.
  60. 60What apparatus is used to prepare chromium(II) ethanoate? Describe how the procedure is carried out1) HCl is slowly added to a flask containing sodium dichromate and zinc mesh. The zinc will reduce the dichromate ions and react with the acid to produce H2(g), which escapes through the rubber tube.
    2) As soon as the solution turns clear blue, the rubber tube is pinched shut so no more H2(g) can escape.
    3) The build up of pressure in the flask will force Cr2+ solution through the glass tube into a flask of sodium ethanoate
    4) A red precipitate of chromium(II) ethanoate will form
    5) The precipitate is filtered and washed with water, then ethanol, then ether (while still keeping the solid in an inert atmosphere)    What apparatus is used to prepare chromium(II) ethanoate? Describe how the procedure is carried out
  61. 61What is a ligand exchange reaction?When two different ligands undergo substitution
  62. 62What happens when ligands of a similar size undergo a ligand exchange reaction?Coordination number of the complex ion doesn't change or the shape
  63. 63Give the colour change when aqueous chromium(III) ions undergo a ligand exchange reaction with excess aqueous ammoniaDark green --> purple
  64. 64What happens when larger charged ligands exchange with small uncharged ligands?There's a change in coordination number and shape as less of the larger ligands can fit around the central metal ion
  65. 65Give the colour change when chloride ions are added to aqueous copper(II) ionspale blue --> yellow
  66. 66Give the colour change when chloride ions are added to aqueous cobalt(II) ionsPale pink --> blue
  67. 67Give the colour change when excess ammonia is added to aqueous copper(II) ions?Pale blue --> deep blue
  68. 68How does carbon monoxide poisoning happen?An oxygen or water molecule in haemoglobin can be replaced in a ligand exchange reaction by CO, forming carboxyhaemoglobin. The strong dative bond that forms between the CO and iron means the reaction is irreversible so oxygen can no longer get transported.
  69. 69Give the equations and colour change for the reaction between aqueous copper(II) ions and hydroxide ions/ammoniapale blue --> blue preciptateGive the equations and colour change for the reaction between aqueous copper(II) ions and hydroxide ions/ammonia
  70. 70Give the equation and colour change for the reaction between copper(II) hydroxide and excess ammoniaBlue precipitate --> deep blueGive the equation and colour change for the reaction between copper(II) hydroxide and excess ammonia
  71. 71Give the equations and colour change for the reaction between aqueous iron(II) ions and hydroxide ions/ammoniapale green--> green precipitate (which darkens on standing as the precipitate is oxidised by water and oxygen in air to form iron(III) hydroxideGive the equations and colour change for the reaction between aqueous iron(II) ions and hydroxide ions/ammonia
  72. 72Give the equations and colour change for the reaction between aqueous iron(III) ions and hydroxide ions/ammoniaYellow --> orange precipitate that darkens on standingGive the equations and colour change for the reaction between aqueous iron(III) ions and hydroxide ions/ammonia
  73. 73Give the equations and colour change for the reaction between aqueous cobalt(II) ions and hydroxide ions/ammoniaPale pink --> blue precipitate which turns brown on standingGive the equations and colour change for the reaction between aqueous cobalt(II) ions and hydroxide ions/ammonia
  74. 74Give the equation and colour change for the reaction between cobalt(II) hydroxide and excess ammoniaBlue precipitate --> yellow brown (goes brown on standing as oxidised to [Co(H2O)6]3+)Give the equation and colour change for the reaction between cobalt(II) hydroxide and excess ammonia
  75. 75Why are transition metals good catalysts?Because they can change oxidation state easily - which means they can transfer electrons to speed up reactions
  76. 76How do heterogeneous catalysts work?By adsorbing reactants at active sites on their surface which allows them to react more easily
  77. 77What happens during the contact process? Include equationsA vanadium(V) oxide catalyst changes its oxidation state reversibly, first reducing to vanadium(IV) oxide as it oxidises sulfur dioxide to sulfur trioxide. Then oxidising back to vanadium(V) oxide by reacting with oxygen.What happens during the contact process? Include equations
  78. 78How do homogeneous catalysts work?By combining with the reactants to form an intermediate, which then reacts to form the product and reform the catalyst. The activation energy needed to form the intermediate is lower than that needed to form the products directly from the reactants.
  79. 79Describe what happens during the reaction between peroxodisulfate ions and iodide ions - include equationsAs both ions are negatively charged, they are very unlikely to collide and react so and iron(II) catalyst is used. This gets oxidised by the peroxydisulfate ions to form iron(III) sulfate ions. The intermediate Fe(III) ions then oxidise the I- ions to iodine and the catalyst is regenerated.Describe what happens during the reaction between peroxodisulfate ions and iodide ions - include equations
  80. 80What is autocatalysis?When a product acts as a catalyst
  81. 81Describe the reaction between ethandioic acid and permanganate ions - include equationsMn2+ catalyses the reaction by first reacting with MnO4- to form Mn3+ ions. The Mn3+ ions then react with C2O4^2- to form carbon dioxide and reform the Mn2+ catalyst.Describe the reaction between ethandioic acid and permanganate ions - include equations
  82. 82How do catalytic converters work?A platinum-rhodium catalyst is used to convert nitrogen oxides and carbon monoxide to nitrogen and carbon dioxide. It works by adsorbing the reactant molecules onto the surface of the solid, activating the molecules so they react more easily (the bonds between the reactants are weakened making them easier to break and reform), then the product molecules are desorbed from the surface.
  83. 83Why is the strength of adsorption important when finding the most appropriate catalyst?The catalyst needs to not adsorb molecules so strongly that the reactive sites of the surface of the metal are inactivated or adsorb molecules not strongly enough to weaken bonds enough.

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AS - Level Chemistry Flashcards on Transition Metals, created by Kayla Price on 16/05/2017.
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Kayla Price
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