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PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY

GENERAL CHEMISTRY. Principles and Modern Applications. TENTH EDITION. PETRUCCI HERRING MADURA BISSONNETTE. 23. The Transition Elements. PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY. The Transition Elements. 23-1 General Properties.

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PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY

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  1. GENERAL CHEMISTRY Principles and Modern Applications TENTH EDITION PETRUCCI HERRING MADURA BISSONNETTE 23 The Transition Elements PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY General Chemistry: Chapter 23

  2. The Transition Elements General Chemistry: Chapter 23

  3. 23-1 General Properties General Chemistry: Chapter 23

  4. Atomic (Metallic) Radii FIGURE 23-1 • Atomic radii of the d-block elements General Chemistry: Chapter 23

  5. Electron Configurations and Oxidation States • The ionization energies are fairly constant across the table. • Standard electrode potentials increase in value across the series. • With the exception of the oxidation of Cu to Cu2+, however, all these elements are more readily oxidized than hydrogen. This means that the metals displace H2 from H+(aq). FIGURE 23-2 • Positive oxidation states of the elements of the first transition series General Chemistry: Chapter 23

  6. Ionic and Covalent Compounds • Ionic and covalent characters are displayed. • MnO is a green ionic solid, mp1785 C. • Mn2O7 boils at r.t. and is highly explosive. • Often occur as polyatomic cations or anions. • VO2+, MnO4-,and Cr2O72- for example. General Chemistry: Chapter 23

  7. Catalytic Activity Ni and Pt are heterogeneous catalysts. Pt, Rh, and Pd are used in catalytic converters. V2O5 is used in conversion of SO2 to SO3. Polyethylene production. General Chemistry: Chapter 23

  8. H2 and C2H4 molecules adsorb onto the metal surface, causing weakening of the H-H bond and the π-bond in C2H4. • H atoms become bonded to carbon atoms, converting C2H4 to C2H6, which desorbs from the metal surface. FIGURE 23-3 Schematic representation of the metal-catalyzed hydrogenation of C2H4 General Chemistry: Chapter 23

  9. Color and Magnetism Color-enhanced image of magnetic domains in a ferromagnetic garnet film. FIGURE 23-4 • Ferromagnetism and paramagnetism compared General Chemistry: Chapter 23

  10. 23-2 Principles of Extractive Metallurgy • Concentration is the first of four steps in the metallurgical process. • Subsequent steps are Roasting, Reduction, and Refining. FIGURE 23-5 • Concentration of ore by flotation

  11. Roasting Δ ZnCO3(s) ZnO(s) + CO2(g) Δ 2 ZnS(s) + 3 O2(g) 2 ZnO(s) + 2 SO2(g) • An ore is roasted (heated to a high temperature) to convert a metal compound to its oxide, which can then be reduced. • For zinc, the commercially important ores are ZnCO3 (smithsonite) and ZnS (sphalerite). • ZnCO3 like the carbonates of the group 2 metals, decomposes to ZnO(s) and when it is strongly heated. • When strongly heated in air, ZnS(s) reacts with O2 producing ZnO(s) and SO2. In modern smelting operations, SO2 is converted to sulfuric acid rather than being vented to the atmosphere.

  12. Reduction Δ ZnO(s) + C (s) Zn (s) + CO(g) Δ ZnC(s) + CO(g) Zn (s) + CO2(g) • Because it is inexpensive and easy to handle, carbon, in the form of coke or powdered coal, is used as the reducing agent whenever possible. Several reactions occur simultaneously in which both C(s) and CO(g) act as reducing agents. The reduction of ZnO is carried out at about 1100oC , a temperature above the boiling point of zinc. The zinc is obtained as a vapor and condensed to the liquid. • The metal produced by chemical reduction is usually not pure enough for its intended uses. Impurities must be removed; that is, the metal must be refined. The refining process chosen depends on the nature of the impurities. The impurities in zinc are mostly Cd and Pb, which can be removed by the fractional distillation of liquid zinc.

  13. Refining ZnO(s) + 2 H+(l) + SO42-(aq) Zn2+(aq) + SO42-(aq) +H2O(l) Cathode: Zn2+(aq) + 2 e- Zn (s) Anode: H2O(l) ½ O2(g) + 2 H+(aq) + 2 e- Unchanged: SO42-(aq) SO42-(aq) Overall: Zn2+(aq) + H2O(l) + SO42-(aq) Zn(s) + 2 H+(aq) + SO42-(aq) + ½ O2(g) General Chemistry: Chapter 23

  14. Zone Refining • As a heating coil moves up the rod of material, melting occurs. Impurities concentrate in the molten zone. • The portion of the rod below the molten zone is purer than the portion in or above the molten zone. • With each successive passage of the heating coil, the rod becomes purer. FIGURE 23-6 • Zone refining General Chemistry: Chapter 23

  15. Zone Refining • The red line shows the freezing points of solutions of impurity B in substance A. • The blue line gives the composition of the solid that freezes from these solutions. • In some cases, the blue line is nearly coincident with the temperature axis. • When a solution of composition l1 is cooled to temperature T1 it freezes to produce a solid of composition s1. If a small quantity of this solid is removed from the solution and melted, it produces a new liquid, l2. The freezing point of l2 is T2 and the composition of the solid freezing from the solution is s2. • With each melting/freezing cycle, the melting point increases and the point representing the composition of the solid moves closer to pure A. In zone refining the melting/freezing cycles are conducted continuously, not in batches as described here. FIGURE 23-7 • The Principle of zone refining

  16. Thermodynamics of Extractive Metallurgy ΔG°(a) 2 C (s) + O2(g) 2 CO(g) ΔG°(b) 2 Zn(s) + O2(g) 2 ZnO(s) -ΔG°(b) 2 ZnO(s) 2 Zn(s) + O2(g) ) Overall: 2 ZnO(s) + 2 C(s) 2 Zn(s) + 2 CO(g) ) -ΔG° = ΔG°(a)- ΔG°(b) General Chemistry: Chapter 23

  17. FIGURE23-8 ΔG as a function of temperature for some reactions of extractive metallurgy General Chemistry: Chapter 23

  18. Alternative Methods to Extractive Metallurgy • Many ores contain several metals and it is not always necessary to separate them. • Fe(CrO2)2 can be reduced to ferrochrome and can be added directly to iron to produce steel. • V2O5 and MnO2 are also added to iron to produce other types of steel. General Chemistry: Chapter 23

  19. 800 C TiO2(s) + C(s) + 2 Cl2(g)  TiCl4(g) + 2 CO(g) • Titanium cannot be produced by reduction with C. 1000 C TiCl4(g) + 2 Mg(s)  2 MgCl2(l) + Ti(s) Kroll Process Vacuum-distilled metallic titanium sponge produced by the Kroll process. General Chemistry: Chapter 23

  20. Electrolytic production of Ti(s) from TiO2(s) General Chemistry: Chapter 23

  21. Metallurgy of Copper 2 Cu2S(l) + 3 O2(g) 2 Cu2O(l) + 2 SO2(g) Slag formed during the smelting of Cu ore. 2 Cu2O(l) + Cu2S(l) 6 Cu(l) + SO2(g) • Concentration of sulfide ore by floatation. • Smelting at 1400°C converts FeS to FeO. • Bottom layer is copper matte: CuS/FeO. • Top layer is Slag (Fe, Ca, Al and Si). • FeO(s) + SiO2(s) → FeSiO3(l) for example. • Conversion (blow air through molten matte) and form iron slag. • Blister copper General Chemistry: Chapter 23

  22. Pyrometallurgical Processes • The roasting – reduction process is known as pyrometallurgy. • Large quantities of waste material produced. • High energy consumption. • Gaseous emission must be controlled. General Chemistry: Chapter 23

  23. Hydrometallurgical Processes • Leaching: Metal ions are extracted from the ore. • Acids, bases and salts may be used. • Oxidation and reduction may also be involved. • Purification and concentration: Adsorption of impurities on activated charcoal or by ion exchange. • Precipitation: Desired ions are precipitated or reduced to the free metal. • Electroanalytical methods are often used. General Chemistry: Chapter 23

  24. 23-3 Metallurgy of Iron and Steel. Fe2O3(s) + 3 CO(g) → 2 Fe(l) + 3 CO2(g) Pouring pig iron. FIGURE 23-9 • Typical blast furnace General Chemistry: Chapter 23

  25. General Chemistry: Chapter 23

  26. Steel • Three fundamental changes from pig iron. • Reduction of the C content. • 3-4% in pig iron • 0-1.5% in steel. • Removal, through slag formation, of: • Si, Mn, P (about 1% in pig iron). • Other minor impurities. • Addition of alloying elements. • Cr, Ni, Mn, V, Mo, and W. • Gives the steel its desired properties. General Chemistry: Chapter 23

  27. General Chemistry: Chapter 23

  28. 23-4 First-Row Transition Elements: Scandium to Manganese • Scandium • Obscure metal, 0.0025% of earths crust. • More abundant than many better known metals. • Limited commercial use. • Produced in kg quantities not tons. • Sc3+ most closely resembles Al3+. • Amphoteric gelatinous hydroxide Sc(OH)3. General Chemistry: Chapter 23

  29. Titanium A computer-generated representation of titanium join implants at the shoulder, elbows, hips, and knees White TiO2(s). mixed with other components to produce the desired color, is the leading pigment used in paints General Chemistry: Chapter 23

  30. TiCl4 is the starting material for Ti compounds. • Used to formulate catalysts for plastics. TiCl4(l) + H2O(l) → TiO2 + 4 HCl • TiO2 opaque, inert and non-toxic. • Paint pigment, paper whitener, additive in glass, ceramics and cosmetics. General Chemistry: Chapter 23

  31. Vanadium +5 +4 +3 +2 FIGURE 23-11 • Some vanadium species in solution • Fairly abundant (0.02%). • Vanadite 3Pb3(VO4)2·PbCl2. • Ferrovanadium 35-95% V in Fe. • Steels are used in applications requiring strength and toughness. • Vandium pentoxide. • Catalyst. • Reversible loss of O from 700-1000°C. • Wide variety of oxidation states. General Chemistry: Chapter 23

  32. General Chemistry: Chapter 23

  33. Chromium Important industrial metal present in earths crust at 0.0122%. Chromite Fe(CrO2)2. Hard, maintains a bright surface, corrosion resistant. General Chemistry: Chapter 23

  34. Cr(H2O)62+, blue 2+ 3+ 3+ (acidic) Cr(H2O)63+, blue (basic) Cr(OH)4-, green 6+ (acidic) Cr2O72-, orange (basic) CrO42-, yellow CrO Cr2O3 CrO3 basicamphotericacidic General Chemistry: Chapter 23

  35. FIGURE 23-12 Decomposition of (NH4)2Cr2O7 General Chemistry: Chapter 23

  36. Oxidation of Cr2+ to Cr3+ occurs rapidly in air. Cr metal dissolved in HCl to give Cr2+ in solution. • The green color is that of the complex ion [CrCl2(H2O)4]+(aq) FIGURE 23-13 Relationship between Cr2+ and Cr3+ General Chemistry: Chapter 23

  37. Manganese ferromanganese • Fairly abundant, about 1% of earths crust. • Pyrolusite MnO2. • Important in steel production. • MnO2 + Fe2O3 + 5 C → Mn + 2 Fe + 5 CO • Mn reacts with O and S which can then be removed through slag formation. • Oxidation states range from +2 to +7. General Chemistry: Chapter 23

  38. FIGURE 23-14 Electrode potential diagrams for manganese General Chemistry: Chapter 23

  39. 23-5 The Iron Triad: Iron, Cobalt and Nickel • Iron: • Annual worldwide production over 500 million tons. • Most important metal in modern civilization. • 4.7% natural abundance. • Cobalt: • 0.0020% natural abundance. • Deposits are reasonably concentrated. • Primarily used in alloys, Co5Sm makes a good magnet. • Nickel: • 24th most abundant element. • Primarily used in alloys, but also for electroplating. General Chemistry: Chapter 23

  40. Oxidation States • The +2 oxidation state is commonly encountered in all three metals. • For cobalt and nickel, the +2 oxidation state is the most stable, but for iron, the +3 is most stable.

  41. Some Reactions of the Iron Triad General Chemistry: Chapter 23

  42. FIGURE 23-15 Structure of some simple carbonyls General Chemistry: Chapter 23

  43. General Chemistry: Chapter 23

  44. 23-6 Group 11: Copper, Silver and Gold • Coinage metals. • Easy to reduce to free metals. • In Mendeleev’s table they were grouped with the alkali metals (single s electron). • Use d electrons in chemical bonding. Gold leaf and copper wire Gold plating on a space antenna General Chemistry: Chapter 23

  45. 23-7 Group 12: Zinc, Cadmium and Mercury • Properties consistent with elements having a full subshell, (n-1)d10ns2. • Mercury is the only room temperature liquid metal. • Relativistic effect: • 6s electrons reach a significant fraction of the speed of light. • Mass of electron increases. • Size of 6s orbital decreases. General Chemistry: Chapter 23

  46. General Chemistry: Chapter 23

  47. Uses of Group 12 Metals • Zinc: • About 30% of production goes to plating on Fe. • Galvanized iron. • About 20% of production goes to alloys. • Brass is a Cu alloy with 20-45% Znand small quantities of Sn, Pb and Fe. • Cadmium: • Bearing alloys. • Low melting solders. A brass seagoing chronometer made by John Harrison in the eighteenth century General Chemistry: Chapter 23

  48. Uses of Group 12 Metals • Mercury • Thermometers, barometers, gas-pressure regulators, electrical relays and switches. • Electrode in the chlor-alkali process. • Vapor in fluorescent tubes and street lamps. • Amalgams formed with most metals. General Chemistry: Chapter 23

  49. General Chemistry: Chapter 23

  50. Mercury and Cadmium Poisoning • Hg may interfere with sulfur containing enzymes. • Organomercurials are more dangerous than elemental mercury. • Some organisms convert Hg2+ compounds to CH3Hg+. • Bioaccumulation and concentration in the food chain. • Cd closely resembles Zn. • Itay-itay kyo or ouch-ouch disease. • Can also cause liver damage, kidney failure and pulmonary disease. General Chemistry: Chapter 23

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