10.4 Titanium Chemistry titanium(II) titanium(III) titanium(IV) oxide redox reactions principal oxidation states extraction

* Advanced Inorganic Chemistry Transition metals 10.4 Titanium Chemistry Doc Brown's

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Doc Brown's Chemistry Periodic Table Revision Notes 10.4

Part 10. Transition Metals 3d-block: 10.4 Titanium Chemistry

Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters Chemistry CIE Chemistry revising courses for pre-university students (equal to US grade 11 and grade 12 and Honours/honors level courses) GCSE Periodic Table * GCSE notes Transition Metals

INORGANIC Part 10 3d block TRANSITION METALS sub-index: 10.1-10.2 Introduction 3d-block Transition Metals * 10.3 Scandium * 10.4 Titanium * 10.5 Vanadium * 10.6 Chromium * 10.7 Manganese * 10.8 Iron * 10.9 Cobalt * 10.10 Nickel * 10.11 Copper * 10.12 Zinc * 10.13 Other Transition Metals e.g. Ag and Pt * Appendix 1. Hydrated salts, acidity of hexa-aqua ions * Appendix 2. Complexes & ligands * Appendix 3. Complexes and isomerism * Appendix 4. Electron configuration & colour theory * Appendix 5. Redox equations, feasibility, E^ø * Appendix 6. Catalysis * Appendix 7. Redox equations * Appendix 8. Stability Constants and entropy changes * Appendix 9. Colorimetric analysis and complex ion formula * Appendix 10 3d block - extended data * Appendix 11 Some 3d-block compounds, complexes, oxidation states & electrode potentials * Appendix 12 Hydroxide complex precipitate 'pictures', formulae and equations

Advanced Level Inorganic Chemistry Periodic Table Index * Part 1 Periodic Table history * Part 2 Electron configurations, spectroscopy, hydrogen spectrum, ionisation energies * Part 3 Period 1 survey H to He * Part 4 Period 2 survey Li to Ne * Part 5 Period 3 survey Na to Ar * Part 6 Period 4 survey K to Kr and important trends down a group * Part 7 s-block Groups 1/2 Alkali Metals/Alkaline Earth Metals * Part 8 p-block Groups 3/13 to 0/18 * Part 9 Group 7/17 The Halogens * Part 10 3d block elements & Transition Metal Series * Part 11 Group & Series data & periodicity plots * All 11 Parts have their own sub-indexes near the top of the pages

10.4. Chemistry of Titanium Ti, Z=22, 1s²2s²2p⁶3s²3p⁶3d²4s²

Ti data table 1 summary * extended titanium data table 2 * Titanium & electrode potential chart of 3d-block
Summary of some complexes-compounds & oxidation states of titanium compared to other 3d-block elements
Titanium is a very important metal for various specialised uses.
Extraction of titanium
- Titanium ore is mainly the oxide TiO₂, which is converted into titanium tetrachloride TiCl₄ by heating with carbon and chlorine. There is no change in oxidation state of titanium in this reaction (+4 in both compounds involved)
- The chloride is then reacted with sodium or magnesium to form titanium metal and sodium chloride or magnesium Chloride.
- This reaction is carried out in an atmosphere of inert argon gas so non of the metals involved becomes oxidised by atmospheric oxygen.
- TiCl₄ + 2Mg ==> Ti + 2MgCl₂ or TiCl₄ + 4Na ==> Ti + 4NaCl
- Overall the titanium oxide ore is reduced to titanium metal (overall O loss, oxide => metal) and the magnesium or sodium acts as a reducing agent.
Titanium alloys are amongst the strongest of metal alloys. There is a GCSE note about the bonding and structure of alloys on another page.
- It is used in aeroplanes, in nuclear reactor alloys and for replacement hip joints.
- With a lighter density of 4.4 g/cm³ compared to steel (~7.9 g/cm³) its just as strong as steel and with the added advantage of being unreactive towards oxygen and water at room temperature so does not suffer the rusting of iron corrosion.
- Titanium(IV) oxide, TiO₂, is an important white pigment used in the paints industry.
  - Note that Ti4+ has a [Ar]3d⁰ structure, hence, with no 3d electrons it is colourless (see colour theory).
Titanium extraction and Ti(IV) CHEMISTRY
It is more difficult to extract from its ore than other more common metals so is not cheap!
- Titanium is extracted from the raw material rutile ore which contains titanium dioxide. This is a high melting ionic compound Ti⁴⁺(O^2-)₂.
- Carbon reduction of the oxide to the metal is not that practical due to titanium carbide formation so the titanium(IV) oxide is initially converted to titanium(IV) chloride which is then reduced to the metal with a more reactive metal in a displacement reaction.
  - Tungsten (W), another transition metal, cannot be obtained from reduction of its oxide for the same reason.
- The rutile titanium oxide ore is heated with carbon and chlorine to make titanium(IV) chloride
  - TiO₂ + 2Cl₂ + C ==> TiCl₄ + CO₂
- After the oxide is converted into TiCl₄ which is then reacted with sodium or magnesium to form titanium metal and sodium chloride or magnesium Chloride. The sodium and magnesium act as the reducing agent in this batch process.
  - This reaction is carried out in an atmosphere of inert argon gas so non of the metals involved becomes oxidised by atmospheric oxygen.
    - TiCl₄ + 2Mg ==> Ti + 2MgCl₂ or TiCl₄ + 4Na ==> Ti + 4NaCl
  - These are examples of metal displacement reactions e.g. the less reactive titanium is displaced by the more reactive sodium or magnesium.
  - Overall the titanium oxide ore is reduced to titanium metal (overall O loss from ox. state +4, oxide => metal with ox. state 0)
  - TiCl₄ is covalent liquid which (i) hydrolyses back to the oxide in water and (ii) dissolves in conc. hydrochloric acid to form the hexachlorotitanate(IV) complex ion.
    - (i) TiCl_4(l) + 2H₂O_(l) ==> TiO_2(s) + 4HCl_(aq/g) (fumes in air!)
    - (ii) TiCl_4(l) + 2Cl^-_(aq) ==> [TiCl₆)]^2-_(aq) (typical complex anion)
- When titanium(IV) compounds are dissolved in water of acid the oxo-cation [TiO]²⁺ is formed.
TITANIUM(III) CHEMISTRY
Titanium(III) compounds can be obtained from Ti(IV) salts by using a zinc/dil. sulphuric acid reduction agent.
- colourless Ti(IV) as [TiO]²⁺ ==> Ti(III) in acid solution giving the purple [Ti(H₂O)₆)]³⁺_(aq) ion.
- but it is readily oxidised back to Ti(IV) by dissolved oxygen from the atmosphere (see electrode potential chart TiO²⁺/Ti³⁺ +0.10V is less positive than O₂+H⁺/H₂O +1.23V in acid solution).
- TiCl₃ is a violet solid.
TITANIUM(II) CHEMISTRY
TiCl₂ is a black solid.
The violet? [Ti(H₂O)₆)]²⁺ ion can be formed by reducing Ti(IV) or Ti(III) with a metal/acid mixture but it is very unstable in redox terms.
Ti²⁺ will reduce water to hydrogen (i.e. oxidised by water to Ti³⁺) and it is rapidly oxidised by air (from dissolved oxygen) and cannot exist in aqueous solution (see electrode potential chart Ti³⁺/Ti²⁺ -0.37V is less positive than O₂/H⁺/H₂O +1.23V in acid solution).
Comparison with a Group 4 metal e.g. tin
- Tin only exhibits oxidation states of +2 and +4, there is no intermediate +3 compounds.
- The compounds are usually colourless.
- Tin is a much weaker metal physically with much lower melting/boiling point.

Scandium * Titanium * Vanadium * Chromium * Manganese * Iron * Cobalt * Nickel * Copper * Zinc * Silver & Platinum

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