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Ch 11. Group 1 (Alkali Metals)

Ch 11. Group 1 (Alkali Metals). D H vap (in kJ/mol) for Metals. Elemental Metals. Synthesis by electrolysis 2 KOH  K (m) + ½ O 2 (g) + H 2 O (l) Sir Humphrey Davy, 1807 (K, Na) Reactivities: M (m) + H 2 O  MOH (aq) + ½ H 2 (g)

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Ch 11. Group 1 (Alkali Metals)

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  1. Ch 11. Group 1 (Alkali Metals)

  2. DHvap (in kJ/mol) for Metals

  3. Elemental Metals Synthesis by electrolysis 2 KOH  K (m) + ½ O2 (g) + H2O (l) Sir Humphrey Davy, 1807 (K, Na) Reactivities: M (m) + H2O  MOH (aq) + ½ H2 (g) Li is rapid; Na to Cs is increasingly violent, explosive

  4. Elemental properties

  5. Pourbaix s-block

  6. Born-Haber approach

  7. Solution and lattice enthalpies

  8. Exchange / Displacement • Large ion salt + small ion salt is better than two salts with large and small ions combined. Example: Salt ΔHL sum CsF 750 NaI 705 1455 kJ/mol CsI 620 NaF 926 1546 • This can help predict some reactions like displacements, ion exchange, thermal stability.

  9. Formation constants with alkali metal cations [M(OH2)n]+ + ether = [M(ether)]+ + n H2O Kf Crown ethers and cryptands

  10. Alkides, electrides en 2 Na(s) Na+ (solv) + Na- (solv) Na+(solv) [Na(crypt)]+Na- (s) en = ethylenediammine, H2NCH2CH2NH2 N2 sodide anion ΔHrxn = 2ΔHat(Na) + I(Na) – Ea(Na) + ΔHsolv, cation + ΔHsolv, anion = 2(108) + 514 - 52 + ? + ? ? We know that ΔHhyd(Na+) = - 400 kJ/mol 2,2,2 crypt

  11. Electrides [Cs(18-C-6)2]+e- Cs(15-C-5)2 Cs+ is the green sphere, electride anion is pink

  12. Li clusters

  13. Ch 12. Group 2 (Alkaline Earths)

  14. Element properties

  15. Be compounds

  16. Organo Be compounds

  17. BeCl2 Organometallics synthesis Hg(CH3)2 + Be (s) → Be(CH3)2 + Hg (l) transmetallation BuLi + BeCl2 → Bu2Be + 2 LiCl (s) halogen exchange BuCl + 2 Li(s) → BuLi + LiCl (s) lithiation BuLi + C6H6 → LiC6H5 + C4H10 Mg(s) + RX → 2 RMgX insertion (Grignard) insertion R2Be+ 2 MgCl2(s)

  18. Thermal stability of metal carbonates • An important industrial reaction involves the thermolysis of metal carbonates to form metal oxides according to: MCO3 (s) → MO (s) + CO2 (g) • DG must be negative for the reaction to proceed. At the lowest reaction temp: DG = 0 and Tmin = DH / DS • DS is positive because gas is liberated. As T increases, DG becomes more negative (i.e. the reaction becomes more favorable). DS depends mainly on DS0{CO2(g)} and is almost independent of M.

  19. Thermal stability of metal carbonates MCO3 (s) → MO (s) + CO2 (g) • Tmin almost directly proportional to DH. • DHL favors formation of the oxide (smaller anion) for smaller cations. • So Tmin for carbonates should increase with cation size.

  20. Carbonate stabilities

  21. Mg2+ chelation with EDTA EDTA = ethylenediaminetetraacetate

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