Group 2 and Reactivity of metals. Group 2. Identification in aqueous solution.

Transcription

1 1 2 Group 2 and H He Li Be B C N O F Ne -1.85V Na Mg Al Si P S Cl Ar V K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe * Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn ** Fr Ra Ac * Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu ** Th Pa U [Ng](ns) 2 [Ng](n-1 d) 10 (ns) 2 Hg: [Xe](4f) 14 (5d) 10 (6s) 2 reactive metals - M s M aq + 2e - - less or poorly reactive hard lewis acids soft lewis acids electrostatic forces covalent O,OH -,CO 3,COO - NH 3 phenolate, RS -, ArN 21/04/2017 IC 11 Group 2 JJ 1 Reactivity of metals oxides heated give metal + O2 oxides are reduced to metals by hydrogen oxides are not reduced to metals by hydrogen Au Pt Pd Ag Hg Cu Bi As Sb Pb Sn Ni Co Cd Fe Cr Zn Mn Al Mg Na Ca Sr Ba K decreasing redox potential > form oxides only indirectly form hydrogen with cold water form hydrogen with hot water or water vapor (at high pressure) form oxides with oxygen form hydrogen with acids 21/04/2017 IC 11 Group 2 JJ 2 Group 2 Identification in aqueous solution textbook fig 12.6 Be : OH - blue solution Mg : CO 3 OH - blue precipitate Ca : CO 3 to C 2 O 4 white ppt Sr : SO 4 to CO 3 to SO 4 white ppt Ba : SO 4 to CO 3 to CrO 4 yellow ppt 21/04/2017 IC 11 Group 2 JJ 3 1

2 Some properties Be Mg Ca Sr Ba Occurence % 6x Ionisation energy / kjxmol ~ Hydration enthalpy Eo/V Ionic radius (r/å) Ionic potential (q/r) Ionic mobility Melting point/ 0 C Atomic radius /Å plm(oh) pl MCO pl MC2O pl MSO4 ~ logk MF logk MEDTA logk Mgly logk MP2O logk MATP /04/2017 IC 11 Group 2 JJ 4 Systematics? Why opposite ionic mobilities and ionic radii? Solubilities of sulfates and hydroxides? Be Mg Ca Sr Ba Ionic mobility Ionic radius /Å plm(oh) pl MSO4 ~ /04/2017 IC 11 Group 2 JJ 5 M Atom Me r (Å) E 0 (V) E 0 (n + /m + ) pkaq logkedta log en3 colour(maqn ) Be He Mg Ne Ca Ar Sr Kr Ba Xe Zn Ar 3d Cd Kr 4d Hg Xe 4f 14 5d /1: Ge Zn 4s Sn Cd 5s /2:.15 Pb Hg 6s /2: Ti Ar 3d /2: -.37 V Ar 3d /2: violet Cr Ar 3d /2: blue Mn Ar 3d /2: light red Fe Ar 3d /2: light green Co Ar 3d /2: red Ni Ar 3d green Cu Ar 3d /1: light blue Pd Kr 4d Pt Xe 4f 14 5d ? Eu Xe 4f /2: -.36 Yb Xe 4f /2: /04/2017 IC 11 Group 2 JJ 6 2

3 Calcium carbonate Calcite (low temperature) Aragonite (high temperature) 21/04/2017 IC 11 Group 2 JJ 7 Calcite Same structure MCO 3 M a/å α Ca o 55 Mg o 58 Fe o 05 Mn o 50 Zn o 27 21/04/2017 IC 11 Group 2 JJ 8 Grignard reagent Formation of C-C bonds using carbanions: R-Cl + Mg R-MgCl R R R-MgCl + C=O R-C-O - -MgCl + R R Also R-Cl + Zn R-ZnCl R 2 Zn 21/04/2017 IC 11 Group 2 JJ 9 3

4 Mg and Ca in life Hydrolytic enzymes Chlorophylls In bones Hydrolysis of polyphosphates : Lewis acid polarisation of bonds O - O P O Mg O - O P O O Calcium pectate (cell wall) In bones, teeth, shells Triggers Striated muscle contraction polyphosphates- carboxylates calmodulin 21/04/2017 IC 11 Group 2 JJ 10 Chlorophylls R =CH 3 Chl. A R =CHO Chl. B R =C 20 H 39 Green colour: 21/04/2017 IC 11 Group 2 JJ 11 End of Chapter problems 22 M + NH 3,l A A s B + C g (slow) M flame: crimson (violet through blue glass) Sr(NH 3 ) 6 Sr(NH 2 ) 2 + H 2 + 4NH 3 (12.9) XCO 3 ; X + H 2 O (0 o C) D (strong base*) D: X + 2OH - + CO 2 (qual. test) X + H 2 XH 2 drying agent (drying agents : MgH 2 CaH 2 ) X = Ba-Ca; X + 2OH - + CO 2 XCO 3 21/04/2017 IC 11 Group 2 JJ 12 4

5 End of Chapter problems 24 CaCl 2 A Polymeric in the solid state 1 BeO B Soda lime 2 Be(OH) 2 C Strong oxidising agent 3 CaO D Qualitative analysis: sulphate test 4 CaF 2 E Hygroscopic used for de-icing 5 BaCl 2 F Amphoteric 6 BeCl 2 G Quicklime 7 MgO 2 H Crystallises with Würtzite structure 8 Ca(OH) 2 /NaOH I A prototype crystal structure 9 21/04/2017 IC 11 Group 2 JJ 13 Kalk - Lime Trivial navne (names) Kalk (limestone) Kridt (chalk) marmor, (marble) CaCO 3 brændt kalk (lime, quick lime) CaO + CO 2 CaO + H 2 O Ca(OH) 2 (0.025M 0 o C, 0.01M 100 o C) Læsket kalk (slaked lime) 21/04/2017 IC 11 Group 2 JJ 14 Group 12 Zn Cd Hg r m /Å o C 1 atm HCP HCP l mp/ o C bp/ o C d/g cm resistivity* E o ΔH o ion r(m )/Å *Mg: /04/2017 IC 11 Group 2 JJ 15 5

6 Group 12 Sphalerite (zinkblende) Galena Cinnober ZnS PbS (NaCl-structure) HgS MS + 3/2O 2 MO + SO 2 ZnO + C Zn + CO (Cd) Zn + CO 2 ZnO + CO HgO (heat) Hg +½O 2 21/04/2017 IC 11 Group 2 JJ 16 Aqueous chemistry H 2 O Cl - OH - NH 3 S xs Zn Zn(H 2 O) 6 ZnCl 4 Zn(OH) 4 Zn(NH 3 ) 4 ZnS ZnS Cd Cd(H 2 O) 6 CdCl 4 Cd(OH) 2 Cd(NH 3 ) 6 CdS CdS Hg Hg(H 2 O) 2 HgCl 4 HgO Hg(NH 3 ) 2 HgS HgS 2 M(NH 3 ) 4 (T d ) + 2NH 3 M(NH 3 ) 6 (O h ) L-Hg(II)-L 21/04/2017 IC 11 Group 2 JJ 17 Group 12 Identification Zn(OH) 4 ZnS white CdS Yellow HgS 2 HgS Black (cinnober) HgS + aqua regia HgCl 2 Hg + Cu Hg,Cu + Cu 21/04/2017 IC 11 Group 2 JJ 18 6

7 Hg 2 In solid (HgCl) n Hg-Hg shorter than in metal Low vibrational frequency 172 cm -1 (HgCl) n diamagnetic E-measurements not consistent with Hg + [Hg 2 ] rather than [Hg + ] 2 in equilibria 21/04/2017 IC 11 Group 2 JJ 19 M + Zn + Zn Zn 2 in fused salts Cd + Cd Cd 2 in fused salts Hg + Hg Hg 2 in aqueous solution K~160 Calomel Hg 2 Cl 2 insoluble Hg 2 (NO 3 ) 2 soluble 21/04/2017 IC 11 Group 2 JJ 20 Zn - acac - - CH 3 O=C CH 2 H + Zn(acac) 2 H 2 O O=C CH 3 [Zn(acac) 2 ] 3 21/04/2017 IC 11 Group 2 JJ 21 7

8 Some hydrolytic enzymes Enzyme Hydrolysis catalysed Metal ion Carboxypeptidase C-terminal peptide residues Zn Leucine aminopeptidase Leucine N-terminal peptide residue Zn Dipeptidase dipeptides Zn Neutral protease peptides Zn, Ca Collagenase collagen Zn Phospholipase C phospholipids Zn β-lactamase II β-lactam ring Zn Thermolysin peptides Zn, Ca Alkaline phophatase phosphate esters Zn Carbonic anhydrase carbondioxide Zn Α-amylase glucosides Zn, Ca Phopholipase A2 phospholipids Ca Inorg. pyrophosphatase pyrophosphate Mg ATPase ATP to ADP Mg 21/04/2017 IC 11 Group 2 JJ 22 Hydrolytic enzymes Carboxypeptidase Leucine aminopeptidase Dipeptidase Neutral protease Collagenase Phospholipase C β-lactamase II Thermolysin Alkaline phophatase Carbonic anhydrase α-amylase Phopholipase A 2 Inorg. Pyrophosphatase ATPase 21/04/2017 IC 11 Group 2 JJ 23 Carbonic anhydrase (H 2 O) 5 ZnOH 2 (H 2 O) 5 ZnOH + + H + pk~9.0 CAZnOH 2 CAZnOH + + H + pk~7.1 21/04/2017 IC 11 Group 2 JJ 24 8

9 Apo- and M- CA CAZn apo CA + Zn apo CA + M CAM CACd inactive in biological systems except in some Diatomers!, but active at higher ph pk 1 ~ /04/2017 IC 11 Group 2 JJ 25 9