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Properties & Applications of Alkaline Earth Metals & Compounds, Exercises of Inorganic Chemistry

Mount St. Mary's University (MSMU)Inorganic Chemistry

An overview of the occurrence, properties, synthesis, technical applications, and alkaline earth metal salts of the alkaline earth metals Be, Mg, Ca, Sr, and Ba. It includes information on their atomic structure, electronic configuration, electronegativity, ionization energy, ionic radius, melting and boiling points, density, flame coloring, and hydration of the alkaline earth cations.

Typology: Exercises

2021/2022

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Slide1

Inorganic Chemistry I

Prof. Dr. T. Jüstel

2. Alkaline Earth Metals

Content

2.1 Occurence

2.2 Properties

2.3 Synthesis

2.4 Technical Applications

2.5 Alkaline Earth Metal Salts

2.6 Be-Compounds

2.7 Mg-Compounds

2.8 Ca-Compounds

2.9 Ba-Compounds

2.10 Biological Aspects

„Alkaline earth metals“

Group

2 or IIA

Partial preview of the text

Download Properties & Applications of Alkaline Earth Metals & Compounds and more Exercises Inorganic Chemistry in PDF only on Docsity!

2. Alkaline Earth MetalsContent2.1 Occurence2.2 Properties2.3 Synthesis2.4 Technical Applications2.5 Alkaline Earth Metal Salts2.6 Be-Compounds2.7 Mg-Compounds2.8 Ca-Compounds2.9 Ba-Compounds2.10 Biological AspectsInorganic Chemistry IProf. Dr. T. Jüstel

Group2 or IIA^4 Be^12 Mg^20 Ca^38 Sr^56 Ba^88 Ra „Alkaline earth metals“

2.1 OccurenceAbundance in the Earth’s Crust. -4 Be: 2.7 10 %, Mg: 1.9%, Ca 3.4%, Sr: 3.6 Inorganic Chemistry IProf. Dr. T. Jüstel

.^ -2^.^ -2^10 %, Ba: 4^10 %

Beryllium (beryllos)^ BeAl[SiO^326

]^ Beryl, emerald, aquamarine 18 greek: Beryll^ Al[BeO]^24

ChrysoberylBeSiOPhenakite 24 Magnesium (magnesia)^ (Ca,Mg)CO

Dolomite 3 town in Asia Minor^ (Mg,Fe)[SiO

]^ Olivine (^4) Mg(OH) [SiO] Talc (^32410) MgAlOSpinel 24 Calcium (calx)^ CaSO^4

Gypsum latin: lime^ CaCO^3

Calcite, aragoniteCaFFluorite (^2) Ca (PO) (OH,F) Apatite 543 Strontium (strontian)^ SrSO^4

Cölestine Place in Scotland^ SrCO^3

Strontianite Barium (barys)^ BaSO^4

Barite greek: heavy^ BaCO^3

Witherite

2.3 SynthesisBy Fused-Salt Electrolysis or by Chemical ReductionBerylliumThrough reduction of BeFwith Mg in graphite crucibles at 1300 °C 2 BeF+ Mg  Be + MgF 2 2 MagnesiumBy fused-salt electrolysis of MgCl at 700 – 800 °C 2 MgCl(l)  Mg(s) + Cl(g) 22 Anhydrous MgCl(s) can be obtained through MgO(s) + Cl 2 Inorganic Chemistry IProf. Dr. T. Jüstel

(g) + C(s)^ ^ MgCl(s) + CO(g) 22 Calcium, StrontiumBy fused-salt electrolysis of the chlorides mixed with the fluorides (eutectic)BariumBy reduction of BaO with Al or Si at 1200 °C in vacuum3 BaO(s) + 2 Al(s)^ ^ AlO(s) + 3 Ba(g)^23 3 BaO(s) + Si(s)^ ^ BaSiO(s) + 2 Ba(g)^3 BaO is obtained by thermal decomposition of BaCO

^ BaO + CO 3 2

2.4 ApplicationsBeryllium • Low neutron absorption cross-section^  Inorganic Chemistry IProf. Dr. T. Jüstel

moderator and reflector for neutrons

-^ Low density^ ^ emission windows for x-ray sources •^ Be-Cu-alloys^ ^ good conductivity and a hardness comparable to that of steel •^ Be-Ni-alloys^ ^ watch spring and surgical instrumentsMagnesium^3 •^ Density = 1.74 g/cm^ Mg-alloys as light metals in the aviation and automotive industry •^ Energy source of the future?: 2 Mg(s) + O

(^0) (g) ⇌ 2 MgO(s) H= -1204 kJ/mol 2 R^ Calcium, Strontium and Barium •^ Calcium is used as a reduction agent in metallurgy •^ Ba is used as getter material in cathode ray tubes and discharge lamps •^ The mixed oxide BaO/SrO/CaO reacts with tungsten at high temperatures and is used asthermionic electron emitter:BaO + W^ ^ BaWO+ 3 Ba (good thermal e^36

-^ -emitter) -^ BaO is used as a additive in glasses to increase the cross-section for x-rays •^ CaO shows white^ ^ thermo-luminescence “limelight”

2.5 Alkaline Earth Metal SaltsThe Hydration of the Alkaline Earth Cations Depends on the Ionic Charge DensityIon Chloride^ Nitrate Inorganic Chemistry IProf. Dr. T. Jüstel

Sulphate 2+^ .MgMgCl6HO^22

..Mg(NO) 6HO^ MgSO7HO 32242 2+^ .Ca CaCl6HO^22

..Ca(NO) 4HO^ CaSO2HO 32242 2+^ .SrSrCl6HO^22

.Sr(NO) 4HO^ SrSO 3224 2+^ .BaBaCl2HO^22 Ba(NO)^ BaSO^32 Enthalpy of solution = hydration enthalpy – lattice enthalpyEntropy of solution = hydration entropy – lattice entropyFree enthalpy of solution = enthalpy of solution – T*entropy of

solution (^000) i.e. G=^ H– T*S^ L^ L^ L

2+^ - M (g) + 2 X(g) HydrationLatticeenthalpyenthalpyEnthalpy+^ - M^ (aq) + 2 X(aq)Enthalpy of solutionMX(s) 2 2+^ - M^ (g) + 2 X(g) HydrationLatticeentropyentropyEntropy+^ - M^ (aq) + 2 X(aq)Entropy of solutionMX(s) 2

2.5 Alkaline Earth Metal SaltsSolubility of Alkaline Earth Metal Salts in WaterHigh Solubility^00 Free enthalpy of solution^ G=^ H– T*L^ L^ Inorganic Chemistry IProf. Dr. T. Jüstel

0 S < 0L^

(^0)  H< 0^0  TS^ > 0 Poor solubility^00 Free enthalpy of solution^ G=^ H– T*L^ L^

0 S > 0L^

(^0)  H> 0^0  TS^ < 0 Example MgCl^2 Lattice enthalpy [kJ/mol] Hydration enthalpy [kJ/mol]

Enthalpy of solution [kJ/mol] -2523^ -^

Lattice entropy [J/Kmol]^ Hydration entropy [J/Kmol]

Entropy of solution [J/Kmol] 360 -^

(^0) Free enthalpy of solution G= -154 kJ/mol – 298 K*(-115 J/Kmol) = - 120 kJ/molL^ (at room temperature = 298 K)

2.7 Mg-CompoundsMost Magnesium Salts Are Hygroscopic and Are Thus Often Used as Desiccants(MgCl , MgSO ) 24 Compounds with hydrogenMg(s) + H(g)  MgH(s) 22 MgH(s) + 2 HO(l)  Mg(OH)^ (s) + 2 H(g) 2222 ionic with rutile-like structureCompounds with halidesMgFas AR coatings of optical glasses (low refractive index n 2 Inorganic Chemistry IProf. Dr. T. Jüstel

= 1.38)D

MgClfor the drying of gases^ ^ forms hexahydrates^2 Compounds with oxygen2 Mg(s) + O(g)^ ^ MgO(s) “magnesia“^2

(^0) H= -1204 kJ/molR^ 2 Mg(s) + CO(g)^ ^ MgO(s) + C(s)^2

(^0) H= -808 kJ/molR^ MgO is used as a neutralisation agent, crucible and oven material as well as a coating forfront panels of plasma displays due to its high emission intensity of secondary electronsMgCl(s) + Ca(OH)^ (s)^ ^ Mg(OH)^ (s) + CaCl^222

(s) 2 2+.Mg-solution + MeCO^ 4 MgCOMg(OH)^23

. 4HO “magnesia alba“ 22

2.8 Ca-CompoundsCa-Compounds Are of Uttermost Importance as Construction Materials in Natureand Manmade Building IndustryCompounds with halides • CaFFlussspat, important in chemistry of fluorine 2 • CaCldesiccant, forms hexahydrates 2 • By-product during soda production: CaCOInorganic Chemistry IProf. Dr. T. Jüstel

2 NaCl^ ^ CaCl+ NaCO 3 2 23 Compounds with oxygen •^ Ca + O^ CaO “burnt lime, quicklime“^2 •^ CaO + CO^ CaCO“lime“^2 3 •^ CaO + HO^ ^ Ca(OH)^ “hydrated lime“^22 •^ Ca(OH)^ + CO^ CaCO+ HO “lime mortar“^2 2 3 2 •^ CaCOas vaterit, aragonite (pearls) and calcite (chalk, limestone, marble)^3 •^ Double spar (calcite) as a crystal is birefringent, meaning the refractive index is isotropicwhich can lead to a duplication of the light beam •^ CaCO(poorly soluble) + HO + CO^3

Structure of calcite Lime stone Foraminifers  Ca(HCO) (readily soluble) 2 32

Slide

2.9 Ba-CompoundsBarium Compounds Are Important Mainly Due to Their High Density and TheirLow Electron Work FunctionReadily soluble Ba salts • BaX (X = F, Cl, Br) highly toxic 2 + 2+ + • BaCO+ 3 H Ba+ CO^ + HO 3 23  mice and rats poison • Ba(NO) as “green fire” ^ pyrotechnics 32 • BaCO CO+ BaO (material for electrodes) 3 2 • BaO + HO  Ba(OH) “barytes water“ 22 • Ba(OH) + CO BaCO+ HO 2 2 3 2 Poorly soluble Ba salts • BaSO contrast agent, white pigment, white standard (spectroscopy) 4 • MeSO+ C  4 CO + MeS (Me = Ca, Sr, Ba) 4 • These Me-sulphides can be transformed into efficient phosphors by doping with EuInorganic Chemistry IProf. Dr. T. Jüstel

2+ ^ Application of MgS:Eu, CaS:Eu, or SrS:Eu as radiation converters

2.10 Biological AspectsMagnesium2+ • Mgis a important ion in bio-inorganic chemistry  Metal centre in chlorophyll (photosynthesis)  In the active centres of ATPases and other enzymes  PCR (Polymerase Chain Reaction) • Intracellular liquidsCalcium • Extracellular liquids • Of importance for blood coagulation and muscle contraction • Exoskeletons: CaCO 3 – Mollusca (mussels, snails) – Cnidaria (corals) • Endoskeletons: Ca (PO)^ (OH,X) with X = F, Cl 543 Inorganic Chemistry IProf. Dr. T. Jüstel

„Luminescence through doping“

-^ Chordata and vertebrata –^ Cephalopoda

Overview Calcium ChemistryOxidation Sates: 0, +IICaCl 2 Inorganic Chemistry IProf. Dr. T. Jüstel

Ca(OH)^2

Ca^ CaO^

2+^.^ Ca (aq)^ CaSO^ 2HO^42

CaCCaCN^2

N^2 CaCO^ Ca(HCO^ )^3

Cl+ 2e 2 O^2
- OH (^) + 2-H SO^4 TC2-CO 3 CO^ /H^ O^22 H O 2 - -NH OH^3