Chemistry - an illustrated guide to science (794128), страница 17
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This iscalled a displacem en t reaction .● Chlorine will displace bromide ionsand iodide ions from solution.● Bromine will displace iodide ions fromsolution.● In a displacement reaction, thehalogen acts as an oxidizing agent andis reduced while the halide ion isoxidized.BromideIodide2 Reaction of chlorine and brominecolorless solution ofchlorine in hexaneorange solution ofbromine in hexane2 Chlorine and bromine● Chlorinecolorless aqueoussolution containingK+ and Br – ionscolorless aqueoussolution containingK+ and Cl – ionsshaking3 Reaction of chlorine and iodinedissolves in the organicsolvent hexane to give a colorless orslightly green solution, depending onconcentration.● Hexane is im m iscible with water.When the two liquids are mixed,hexane forms a layer above water.● When solutions of chlorine in hexaneand potassium bromide in water areshaken together, chlorine displacesbromide ions from the aqueoussolution.
Bromine is more soluble inhexane than in water, and an orangelayer of bromine in hexane forms:2KBr + Cl 2 ➞ 2KCl + Br 22Br - + Cl 2 ➞ 2Cl - + Br 23 Chlorine and iodinepink/ purple solutionof iodine in hexanecolorless aqueoussolution containingK+ and I – ionscolorless aqueoussolution containingK+ and Cl – ionssolutions of chlorine in hexaneand potassium iodide in water areshaken together, chlorine displacesiodide ions from the aqueous solution.Iodine is more soluble in hexane thanin water, and a pink-purple layer ofiodine in hexane forms:2KI + Cl 2 ➞ 2KCl + I 22I - + Cl 2 ➞ 2Cl - + I 2shaking© Diagram Visual Information Ltd.● Whencolorless solution ofchlorine in hexane98PATTERNS—METALSKey wordsaluminumcoppergoldironleadplatinumsilveruraniumzincWorld distributionof metals1 Gold, sliver, platinum, and uranium1 Gold, sliver, platinum,and uranium● Gold:South Africa, USA, Canada,Russia● Silver: USA, South America● Platin u m : South Africa, USA, SouthAmerica● Uran iu m : North America, Europe,Central and South Africa, Australia2 Aluminum and copper● Alu m in u m :South America, Jamaica,West Africa, Russia, India, Australia● Copper: North America, Central andSouth Africa, Europe, Russiagoldsilverplatinumuranium2 Aluminum and copper3 Iron, zinc, and lead● Iron :North and South America,Russia, Europe, Angola, Australia● Zin c and lead: USA, Europe, Australia,Russiaaluminumcopper© Diagram Visual Information Ltd.3 Iron, zinc, and leadironzinc and lead99Main ores of metalsPATTERNS—METALSChemical namefor ore(s)Formula of ore(s)Key wordsaluminumbauxitealuminum oxideAl 2O3.2H2Ogrademineraloreoxidesulfidechromiumchromiteiron chromium oxideFeCr 2O4copperchalcopyritebornitechalcocitecopper iron sulfidecopper iron sulfidecopper(I) sulfideCuFeS2Cu5FeS4Cu2SOres● Anore is a m in eral from which ametal (or non-metal) can be extracted.● Metal ores are often metal oxides ormetal su lfides.● A metal may be present in a range ofdifferent minerals, but not all mineralswill be suitable sources of that metal.Recovering oresironhaematitemagnetiteiron(III) oxideiron(II)iron(III) oxideFe2O3Fe3O4leadgalenacerussiteanglesitelead(II) sulfidelead(II) carbonatelead(II) sulfatePbSPbCO3PbSO4magnesiummagnesitemagnesium carbonateMgCO3mercurycinnabarmercury sulfideHgSsilverargentitesilver sulfideAg2Ssodiumsaltsodium chlorideNaCltincassiteritetin oxideSnO2titaniumrutileilmenitetitanium oxideiron titanium oxideTiO2FeTiO3uraniumuraniniteuranium oxideUO2zinczinc blendecalaminezinc sulfidezinc carbonateZnSZnCO3● Tobe appropriate for mining, an oremust contain minerals that arevaluable and that are concentratedenough to be mined profitably.
It mustalso be economically viable to extractthe ore from waste rock.● Mineral deposits that are economicallyrecoverable are called ore deposits.Not all mineral deposits are suitablefor recovery. Some may be too low ingrade (the concentration of the ore inthe rock) or technically impossible toextract.Formation● Theprocess of ore formation is calledore genesis.● Ore genesis involves a variety ofgeological, internal, hydrothermal,metamorphic, and surficial processes.© Diagram Visual Information Ltd.MetalCommon namefor ore(s)10 0PATTERNS—METALS1 Position in the periodic tableKey wordsalkali metalsboiling pointgroup 1melting pointorbitalThe group 1 metalsradioactiveshellLiNa1 Position in periodic table● Thegrou p 1 metals occupy the firstcolumn of the periodic table.Historically, they were known as thealkali m etals because they all reactwith water to give alkaline solutions.● The elements include lithium, sodium,potassium, rubidium, and cesium.Francium lies below cesium in theperiodic table.
However, it is notconsidered when discussing the groupbecause it is radioactive, and little isknown of its chemistry.Kmetal reactivity increasesdown the groupRbmetal reactivity decreasesacross a periodCs2 Electron-shell structure21senergy level2 Electron-shell structure● Theelectrons surrounding the nucleusof an atom are arranged in a series oforbitals, areas around the atom wherethere is a high probability of finding anelectron.
Orbitals are grouped in aseries of shells (energy levels) at agradually increasing distance from thenucleus. Different orbitals havedifferent shapes: s orbitals arespherically symmetric; p orbitals pointin a particular direction; and d orbitalshave complicated shapes. Scientistsdescribe an atom by describing theorbital structure. Thus, as the tableindicates, sodium has 2s orbitals in thefirst shell, 2s and 6p orbitals in thesecond shell, and 1s orbital in thethird shell.3 Physical propertiestype of orbitalLi1s22s1Na1s2 2s2 2p 6 3s1K1s2 2s2 2p 6 3s2 3p 6 4s1Rb1s2 2s2 2p 6 3s2 3p 6 4s2 3d 10 4p 6 5s1Cs1s2 2s2 2p 6 3s2 3p 6 4s2 3d 10 4p 6 5s2 4d 10 5p 6 6s13 Physical properties of group I elementscompared with a typical metal● Reading© Diagram Visual Information Ltd.down the group, the m eltin gpoin t decreases, the boilin g poin tincreases, the density increases, andthe hardness decreases.number of electronsin orbitalGroup 1elementLithiumSodiumPotassiumRubidiumCesiumLiNaKRbCsm.p./ °Cb.p./ °CDensity/ g cm–3Hardness/ MohConductivityΩ–1cm–118098643929133688375970 06690.530.970.861.531.880.60.40.50.30.21170 02380 01640 0910 020 0 0153030 0 078604–51130 0Typical m etalIronFe10 1The group 1 metals:sodium1 Reaction of sodium hydroxide (NaOH)with hydrochloric acid (HCl)PATTERNS—METALSKey words2 Sodium burnsreadily in chlorineor oxygencathodeelectrolysissalttitration1 Reaction of NaOHwith HClpipetteburetteblueindicatoracidacid-baseindicatoralkalianode● Group1 hydroxides are alkalis.They can be used to form salts byneutralizing them with acids in aprocess call titration .
Sodium chlorideis made by neutralizing sodiumhydroxide with hydrochloric acid.HydrochloricacidNaOH + HCl ➞ NaCl + H2Osodiumhydroxidesolution● A givenvolume of sodium hydroxidesolution is put into a conical flask.● A few drops of an acid–base in dicatorare added to the sodium hydroxidesolution. The indicator is a differentcolor in acids and alkalis.● Hydrochloric acid is run into thesodium hydroxide solution buretteuntil the indicator just changes color.sodium chlorideindicator turnsgreenSodium hydroxidesolution is placed Hydrochloric acidin the beakeris introduced intothe sodiumhydroxide solution2 Burning sodiumResults of thereaction● Sodiumburns vigorously in chlorine toform sodium chloride:3 Sodium reacts with nitrogen gas2Na + Cl 2 ➞ 2NaCl● Sodiumalso burns vigorously inoxygen to form sodium oxide:sodiumnitrogen4Na + O2 ➞ 2Na2O3 Sodium and nitrogen● Whenheated in a stream of nitrogen,sodium reacts to form sodium nitride:heat6Na + N2 ➞ 2Na3N4 Commercial preparation of sodium4 Preparation of sodium● Sodiumis obtained by the electrolysisof molten sodium chloride in a Downscell.
Sodium is discharged at thenegative electrode (cathode):chlorine gasNa+ + e- ➞ Namolten sodiumchlorideThe product at the positive electrode(an ode) is chlorine gas:2Cl - ➞ Cl 2 + 2e-circularcathodeanode© Diagram Visual Information Ltd.liquid sodium10 2PATTERNS—METALS1 Position in the periodic tableKey wordsalkaline earthmetalsgroup 2ionThe group 2 metalsionization energyorbitalradioactivereactivityBeMg1 Position in periodic table● Thegrou p 2 metals occupy the secondcolumn of the periodic table. Theyinclude beryllium, magnesium, calcium,strontium, and barium.
Radium, whichlies below barium, is not usuallyconsidered when discussing the groupbecause it is radioactive. Historically,group 2 metals were known as thealkalin e earth m etals because all butberyllium react with water to givealkaline solutions.● The atomic radius and, therefore, thesize of the atoms increases goingdown the group.CaSrBa2 Electron-shell structure21senergy level2 Electron-shell structurecan describe an atom bydescribing its electron-shell structure(see page 150).● All group 2 elements form ion s bylosing two outer electrons. The energyneeded to do this is the sum of thefirst and second ion ization en ergies,i.e., the energy needed to remove thefirst electron and the second electron.● Going down the group, there is anincrease in the number of orbitals ofelectrons.
This affects the value of theionization energy in two ways: 1) thetwo outer electrons are further fromthe positively charged nucleus, and 2)there are more layers of electronsbetween the nucleus and the outerelectrons, which partially shields theouter electrons from the nucleus.Consequently, going down the group,less energy is needed to remove theouter two electrons, and the metalsbecome progressively more reactive.© Diagram Visual Information Ltd.● Scientists3 Reactivitywith the group 1 metals, thereactivity of the group 2 metalsincreases going down the group.● The group 2 metals have similarchemical properties as group 1 metals;however, the reactivity of group 2metals in the same period is less.number of electronsin orbitaltype of orbitalBe1s22s2Mg1s2 2s2 2p 6 3s2Ca1s2 2s2 2p 6 3s2 3p 6 4s2Sr1s2 2s2 2p 6 3s2 3p 6 4s2 3d 10 4p 6 5s2Ba1s2 2s2 2p 6 3s2 3p 6 4s2 3d 10 4p 6 5s2 4d 10 5p 6 6s23 Reactivity comparison with group IIII2LiBe3NaMg4KCa● Asreactivity decreases goingacross a periodreactivity increasesgoing down a group10 3The group 2 metals:general reactions1 Sodium and waterPATTERNS—METALSKey wordsalkalicarbonic acidgroup 2hydrochloric acidinsoluble2 Calcium and waterlimewatersoluble1 Sodium and water● Sodiumreacts vigorously with water toform sodium hydroxide solution (astrong alkali) and hydrogen gas.pH = 7bubblespH = 7pH = 12pH = 10bubblesCa + 2H2O =Ca(OH) 2 + H2Suspension→Solution→2Na + 2H2O =2Na(OH) + H23 Production of “rainwater”4 Effect of rainfall onfresh waterrain● Calciumreacts less vigorously withwater than sodium to form calciumhydroxide solution and hydrogen gas.● Calcium hydroxide is less solu ble thansodium hydroxide and forms a weakalkali solution containing suspendedparticles of undissolved solid.3 Rainwater● Naturallyoccurring rainwater is alwaysweakly acidic because carbon dioxidefrom the air dissolves in it, formingweak carbon ic acid, H2CO3.CO2 + H2O = H2CO3CO2 gas2 Calcium and water4 Effect of rainfall● WhatlimestonerocksBubble unknowngas into limewaterCa(OH2 )Result if thegas is CO2stream of water containingdissolved solidsrocks with soluble group 2 compounds(e.g., CaCl 2, CaSO)rain flows over rocks, grou p 2metal compounds dissolve in it,resulting in water that containsdissolved solids.● Magnesium and calcium carbonatesare effectively in solu ble in water, butthey react with rainwater, because it isacidic, to form solublehydrogencarbonates.5 Ca(OH) 2 testGas6 Barium chloride (BaCl2)test for metal sulfatesmilkysuspensionCaCO3● Lim ewater,an aqueous solution ofcalcium hydroxide, is used to test forcarbon dioxide.● When carbon dioxide is bubbled intolimewater, it turns milky due to theformation of insoluble calciumcarbonate, CaCo3.6 BaCl2 test● TheBubble unknowngas into limewaterCa(OH2 )Result if thegas is CO2Add barium chloridedissolved inhydrochloric acidto the knownsolutionA white suspensionis produced if thesolution containsa sulfatetest solution is first acidified withdilute hydrochloric acid, and a fewdrops of barium chloride solution arethen added.
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