Periodic Table - Transition Metal Chemistry - Doc Brown's Chemistry  Revising Advanced Level Inorganic Chemistry Periodic Table Revision Notes

 Appendix 12 Complex & hydroxide precipitate 'pictures'

Some 'test tube' pictures of a variety of soluble transition metal complex ions and precipitates of insoluble complexes.

GCSE/IGCSE Periodic Table Revision Notes  *  GCSE/IGCSE Transition Metals Revision Notes

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced level inorganic chemistry students US K12 grade 11 grade 12 inorganic chemistry - 3d block transition metal chemistry Sc Ti V Cr Mn Fe Co Ni Cu Zn

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

Appendix 12 PICTURES of PRECIPITATES and COMPLEX FORMATION

Prior to, and with, excess reagent for selected 3d block aqueous ions.

They can be used as simple tests for identifying transition metal ions.

Text and formula summary of these reactions of 3d block ions is given below but there are more details in most cases in the notes for each metal for ...

[M(H₂O)₆]ⁿ⁺ where M = metal, n = 2 or 3 and Al³⁺ for comparison (See Chemical Tests for more precipitates)

... and many are useful simple tests to identify metal ions (ppt. = precipitate, gel. = gelatinous)

For detailed equations of these reactions go to the specific chemistry sections for that metal via the index below

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

The comparison equations for the aluminium ion (NOT a 3d block metal)

• The addition of limited amounts of the bases sodium hydroxide or ammonia solution to an aluminium salt solution.

  • [Al(H₂O)₆]³⁺_(aq) + 3OH^–_(aq) ==> [Al(H₂O)₃(OH)₃]_(s) + 3H₂O_(aq)

  • A white gelatinous precipitate of aluminium hydroxide is formed.

    • Simplified equation: Al³⁺_(aq) + 3OH^–_(aq) ==> Al(OH)_3(s)

• The further addition of excess sodium hydroxide or ammonia solution.

  • With excess ammonia there is no effect, but with excess sodium hydroxide the aluminium hydroxide dissolves to form a soluble aluminate complex anion – therefore exhibiting amphoteric behaviour. since the hydroxide will also dissolve in acids (paragraph below NaOH equation).

  • [Al(H₂O)₃(OH)₃]_(s) + 3OH^–_(aq) ==> *[Al(OH)₆]^3–_(aq) + 3H₂O_(aq)

    • Simplified equation: Al(OH)_3(s) + 3OH^–_(aq) ==> *[Al(OH)₆]^3–_(aq)

    • *The products will be an equilibrium mixture including [Al(H₂O)₂(OH)₄]^–_(aq) and [Al(H₂O)(OH)₅]^2–_(aq) too.

    • You could write the equation in terms of forming these species too and any of the three possibilities should get you the marks.

  • To complete the 'amphoteric' picture of aluminium hydroxide we consider it dissolving in mineral acids to form typical salts e.g. aluminium chloride, aluminium nitrate and aluminium sulfate.

    • Al(OH)_3(s) + 3HCl_(aq) ==> AlCl_3(aq) + 3H₂O_(l)

    • Al(OH)_3(s) + 3HNO_3(aq) ==> Al(NO₃)_3(aq) + 3H₂O_(l)

    • 2Al(OH)_3(s) + 3H₂SO_4(aq) ==> Al₂(SO₄)_3(aq) + 6H₂O_(l)

• The addition of sodium carbonate solution to an aluminium salt solution.

  • Bubbles of carbon dioxide and a white gelatinous precipitate of aluminium hydroxide are formed.

    • 2[Al(H₂O)₆]³⁺_(aq) + 3CO₃^2–_(aq) ==> 2[Al(H₂O)₃(OH)₃]_(s) + 3CO_2(g) + 3H₂O_(aq)

    • There several equation 'permutations' to represent this quite complicated reaction, so I've just composed one that shows the formation of both observed products. Since sodium carbonate solution is alkaline you can legitimately write a hydroxide ppt. equation as for sodium hydroxide above but it doesn't show the formation of carbon dioxide.

      • You can write an equation to show the formation of carbon dioxide leaving a soluble cationic complex of aluminium in solution and this equation fits in well with the acid–base nature of this reaction.

        • [Al(H₂O)₆]³⁺_(aq) + CO₃^2–_(aq) ==> 2[Al(H₂O)₄(OH)₂]⁺_(aq) + CO_2(g) + 3H₂O_(aq)

        • This equation shows the hexaaquaaluminium ion acting as a Bronsted–Lowry acid donating two protons to the carbonate ion (B–L base) to form carbon dioxide and water.

    • This reaction shows why 'aluminium carbonate' 'Al₂(CO₃)₃' cannot exist. The hydrated highly charged central metal ion is too acidic to co–exist with a carbonate ion. The same situation applies to the chromium(III) Cr³⁺ and iron(III) Fe³⁺ ions i.e. no chromium(III) carbonate or iron(III) carbonate exists. However with a lesser charged, lesser acidic ion, carbonates can exist, so there is an iron(II) carbonate FeCO₃.

• The addition of excess sodium carbonate solution has no further effect. Sodium carbonate is too weak a base to effect the amphoteric nature of aluminium hydroxide and dissolve the aluminium hydroxide precipitate.

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

Introduction 3d–block Transition Metals * 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

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