Chemistry - an illustrated guide to science (794128), страница 15
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Su lfu r burning2. Conversion of su lfu r dioxide tosu lfu r trioxide3. Absorption of sulfur trioxide to formsulfuric acid.1 Sulfur burningO2● Moltensulfur is sprayed into a furnaceand burned in a blast of dry air. Thereaction is very exotherm ic, and thereaction temperature rises to over1,000°C. The mixture of gases,containing sulfur dioxide and oxygen,is cooled before conversion.420°CReaction bed 1600°CPreparation of sulfuric acid63% conversion450°C2 ConversionReaction bed 2510°C● TheHeatexchangers84% conversion450°C98% H2SO4Reaction bed 3475°CSO393% conversionIntermediateabsorber420°CremainingSO3Reaction bed 4435°C99.5% H2SO499.5% conversionconversion of sulfur dioxide intosulfur trioxide is an exothermicreaction.
The forward reaction isfavored by a low temperature.However, this would also reduce therate of reaction, so it would takelonger for the reaction mixture toreach equ ilibriu m .● The reaction is carried out attemperatures between 420–620°C inthe presence of a vanadium(V) oxidecatalyst.● Modern converters consist of fourreaction beds.
The reaction mixture iscooled after passing through each ofthe first two beds in order to maximizeconversion in subsequent beds.3 Absorption3 AbsorptionH2SO4 (1) + SO3(g)H2S2O7(1)H2S2O7(1) + H2O(1)→ 2H2SO4 (1)trioxide is removed andabsorbed after the reaction mixturehas passed through both the third andfourth beds.● Sulfur trioxide is absorbed into98 percent sulfuric acid to form99.5 percent sulfuric acid, which issometimes referred to as oleum andgiven the chemical formula H2S2O7.● Oleum is then diluted to give 98percent sulfuric acid.© Diagram Visual Information Ltd.● SulfurSO3(g)to final absorber86PATTERNS—NON-METALSKey wordscatalystoresulfidesulfursulfur dioxidesulfuric acidsulfur trioxideIndustrial preparation ofsulfuric acid (the contactprocess): schematicIndustrial preparation of sulfuric acidPreparing sulfuric acid© Diagram Visual Information Ltd.● Thesu lfu r needed for themanufacture of su lfu ric acid isobtained either directly from theground or as a by-product of otherindustrial processes, such as therefining of metal su lfide ores and therefining of crude oil.● An excess of dry air is used to ensurethere is sufficient oxygen remaining inthe reaction mixture for theconversion of su lfu r dioxide to su lfu rtrioxide.● The vanadium(V) oxide (vanadiumpentoxide) catalyst is activated bypotassium sulfate on a silica support.
Itis generally in the form of smallcylindrical pellets that ensure a largesurface area for reaction. The catalystis inactive below about 380°C and hasan optimum working temperaturebetween 420–620°C.● The catalyst pellets are packed ontoperforated plate supports to formreaction beds. In a modern converter,there four reaction beds, eachconsisting of a layer of catalyst pelletsabout 0.6 m deep.● A conversion of 99.5 percent of sulfurdioxide to sulfur trioxide is essentialfor both economic and environmentalreasons. This can only be attained byremoving heat between reaction bedsand by removing the sulfur trioxideproduced between the third andfourth beds.● The mixture of gases that remain afterabsorption consists mostly of nitrogen,together with a small proportion ofoxygen and traces of sulfur dioxide.The gases are filtered to remove anysulfuric acid before being released intothe atmosphere at high level via astack.● Sulfuric acid is used in a wide varietyof industries.
Important uses includethe manufacture of general chemicals,paints and pigments, detergents andsoaps, and phosphatic fertilizers.SulfurSulfurburningReactorTemperature:420 –620 °CPressure:a littlemore thanatmosphereCatalyst:vanadium(V) oxideExcessdry airSO2 + 0 2HeatexchangersSO3, S0 2 + depleted airAbsorbtion into98% sulfuricacid99.5% sulfuricacidWaterDilutionProduct98%sulfuric acidWaste gases95% nitrogen5% oxygensulfur dioxide87Affinity of concentratedsulfuric acid for waterPATTERNS—NON-METALSKey wordsalcoholalkenecarboxylic acidcatalystester1 Sulfuric acid and atmospheric waterH2 OatmosphericwaterH2 OH2 OH2 OH2 OH2 Oconcentratedsulfuric acidseveraldayslaterH2 OH2SO4H2 SO42 Illustrating sulfuric acid’s affinity for watersteamsulfuric acidaddedsulfuric acid1 Sulfuric acid andatmospheric water● Concentratedsu lfu ric acid will absorbwater from the air.● The level of liquid in a beakercontaining concentrated sulfuric acidrises as water is absorbed and the acidbecomes more dilute.2 Sulfuric acid’s affinityfor water● Concentratedmass ofcarbonsulfuric acid will removethe elements of water from organicchemicals such as sucrose ( C12H22O11).● When concentrated sulfuric acid ispoured onto sucrose, the crystallinewhite sucrose turns into a blackamorphous mass of carbon.sucroseReaction withatmospheric water3 Drying gasesReaction withsugar solution● Concentrated3 Drying gaseswetgasdrygassulfuric acid can be usedto dry gases, such as hydrogen.
Thegas is bubbled through the acid in asuitable container.● Some gases, such as ammonia, reactwith concentrated sulfuric acid andcannot be dried in this way.4 Forming esters andalkenes● Concentratedconcentratedsulfiric acidsulfuric acid is used as acatalyst in the formation of esters fromcarboxylic acids and alcohols.Concentrated sulfuric acid removesthe elements of water from alcohols toform alken es:R-CH2-CH2OH-H2O➞R-CH=CH2ORO–H2OCOHCarboxylic acidHRCOR1AlcoholOR1Ester© Diagram Visual Information Ltd.4 Forming esters and alkenes88PATTERNS—NON-METALSKey wordshydrogenperoxidehydrogensulfideoxidizing agentoxygenredox reactionreductionsulfursulfur dioxide1 Common redox reactions1 Common redox reactions8H2S + 8Cl 2S8 + 16HClHydrogen sulfide reduces chlorine gas● Oxidation2 Sulfuric acid and sulfatereactions2KOH + 2MnO2 + 2O2Hydrogen peroxide reduces potassium manganate(VII) solutionSO2 + 2FeCl 3 + 2H2O2FeCl 2 + 2HCl + H2SO4Sulfur oxide reduces iron chloride solutionO2 + 2SO22SO3Oxygen oxidizes sulfur dioxideCu + 2H2SO4CUSO4 + H2O + SO2Concentrated sulfuric acid oxidizes copper2 Sulfuric acid and sulfate reactionsAcid + metal oxide=H2SO4 + MgOAcid + metal hydroxideSalt + waterMgSO4 + H2O=H2SO4 + Cu(OH) 2Salt + waterCuSO4 + 2H2O● Sulfuric© Diagram Visual Information Ltd.acid reacts with metal oxidesto form sulfates and water.● Sulfuric acid reacts with metalhydroxides to form sulfates and water● Sulfuric acid reacts with metalcarbonates to form salts, carbondioxide, and water● In all of these reactions, no oxidationor reduction takes place.
The chargeon the metal ion in the oxide,hydroxide, and carbonate is the sameas it is in the sulfate.H2O2 + 3KMnO4→reactions and redu ctionreactions are more accuratelydescribed as redox reaction s becausethey cannot occur in isolation. Onesubstance is reduced and another isoxidized at the same time.● Hydrogen su lfide reduces chlorine gasto chloride ions.
The sulfide isoxidized to elemental su lfu r:Cl 2 + 2e- ➞ 2Cl - reductionS2- ➞ S + 2eoxidation● Hydrogen peroxide is an oxidizingagent but is itself oxidized by a morepowerful oxidizing agent such aspotassium manganate(VII).● Su lfu r dioxide is a reducing agentboth in the gaseous form and inaqueous solution. It reduces iron(III)to iron(II) while being itself oxidizedto a sulfate:Fe3+ + e- ➞ Fe2+ reduction● Sulfur dioxide can be oxidized tosulfur trioxide by reaction with oxygen .● Copper reacts with concentratedsulfuric acid.
In this reaction, theconcentrated sulfuric acid acts as anoxidizing agent, oxidizing coppermetal to copper(II). The sulfuric acidis itself reduced to sulfur dioxide:Cu ➞ Cu2+ + 2e- oxidationOxygen and sulfur:oxidation and reductionAcid + metal carbonateH2SO4 + ZnCO3=Salt + carbon dioxide + waterZnSO4 + CO2 + H2O89Basic reactions ofoxygenPATTERNS—NON-METALSKey wordsalkaliamphotericcationhydroxideoxide1 ReactionsOxidizes other elements2H2O2Na2ONa2O28SO2P4 O102CuO1 Reactions● Oxygenreacts with both metals andnon-metals to form oxides.● Group 1 and group 2 metals oftenform more than one oxide:Na2O sodium monoxideNa2O2 sodium peroxideNaO2 sodium dioxide● Tran sition m etals form oxides inwhich the metal exhibits differentvalen cy states:Cu2O copper(I) oxideCuOcopper(II) oxide● Non-metallic elements also form morethan one oxide:P4 O6 phosphorus(III) oxideP4 O10 phosphorus(V) oxideOxidizes other elements2CO + O22SO2 + O24NH3 + 5O22CO22SO34NO + 6H2O2 The hydridesbcd2Na +H2 O +H2 O +H2 O +H2 O +→Watera2H2OHClNH3CO2SO22NaOH + H2H3O+ + Cl –NH4+ + OH–H2CO3H2SO3● WaterOxidizes other elementsfgBaO2 + H2SO4H2O4 + 2FeCl 2 + 2HClH2O2 + 2KMnO4→eH2O2 + BaO42FeCl 3 + 2H2O2KOH + 2MnO2 + 2O23 The oxidesOxidizes other elementshiCuO + H2SO4ZnO + H2SO4ZnO + 2NaOHCuSO4 + H2OZnSO4 + H2ONa2Zn(CH) 4 + H2OOxidizes other elementsjkabcdSO2, CO2H2O, COoxidizes reactive metalsaccepts protons from acidsgives protons to basesreacts with non-metal oxidesefghpreparationan oxiding agenta reducing agentbasic2 The hydridesi amphotericj acidick neutralreacts with group 1 and group 2metals to give the metal hydroxideand hydrogen.
In these reactions, themetal is oxidized to a metal cation andthe water is reduced:M ➞ M + and M ➞ M 2+● In the Brønsted-Lowry theory of acidsand bases, an acid is defined as asubstance that donates protons and abase as a substance that acceptsprotons. Water acts as both an acidand a base.● Non-metallic oxides dissolve in waterto form acids:H2CO3 H+ + HCO3- carbonic acidH2SO3 H+ + HSO3 sulfurous acid3 The oxides● Metaloxides are basic and react withacids to form salts and water.● Non-metallic oxides are acidic orneutral.● Some metal oxides are am photeric:they react with both acids and alkalis.© Diagram Visual Information Ltd.2H2 + O24Na + O22Na + O2S8 + 8O2P4 + 5O22Cu + O2oxygentransition metalsvalency90sulfidesulfursulfur dioxidesulfuric acid1 Reactions of sulfur● Su lfu rreacts with most metals andhydrogen to form su lfides.
Metalsulfides react with acids to givehydrogen su lfide:FeS(s) + 2HCl(aq) ➞FeCl 2(aq) + H2S(g)● Sulfurcombines with non-metals suchas oxygen and chlorine.● Su lfu r dioxide is formed by thereaction between concentratedsu lfu ric acid and sulfur.sulfide dissolves in water toform a weak acid.● Group 1 metal sulfides are soluble inwater, however, other metal sulfidesare only sparingly soluble and formcharacteristically colored precipitates.Moist lead(II) ethanoate paper turnsblack in the presence of hydrogensulfide due to the formation of leadsulfide:● Hydrogensulfide and sulfur dioxideundergo a redox reaction to formelemental sulfur.3 The oxides SO2 and SO3● Sulfurdioxide dissolves in water toform sulfurous acid, a weak acid.● Sulfur dioxide is oxidized to sulfurtrioxide.● Sulfur trioxide dissolves in water toform sulfuric acid, a strong acid.4 The hydroxy compound© Diagram Visual Information Ltd.● Concentratedsulfuric acid is a strongoxidizin g agen t and will oxidize bothmetals and non-metals.● Concentrated sulfuric acid is a strongdehyratin g agen t and will removewater or the elements of water.FeSCu2SH2 SReduces other elements elementsS + O22S + Cl 2SO2S2Cl 2Reduces some compounds3S + 2H2SO43SO2 + 2H2O2 The hydridesIs a sparingly soluble acidic gasH3O+ + HS–H2 S + H 2 OIs a reducing agent2H2S + SO22H2O + 3SCauses precipitation of insoluble metel sulfidesCuSO4 + H2SCuS + H2SO43 The oxides SO2 and SO3Is a sparingly soluble acidic gasSO2 + H2OH2SO3Is reducing agent2SO2 + O2SO2 + 2H2S2SO33S + 2H2O→Pb 2+ + S2- ➞ PbSFe + S2Cu + SH2 + S→● HydrogenOxidizes some elements→2 The hydrides1 Reactions of sulfurSO3 is very acidicSO3 + H2OH2SO44 The hydroxy compoundAs a strong acidH3O+ + HSO4–H2SO4 + H2OAs an oxidizing agent→dehydratingagenthydrogen sulfideoxidizing agentredox reaction2H2SO4 + CCu + 2H2SO4CO2 + 2SO2 + 2H2OCuSO4 + SO2 + 2H2O→Key wordsBasic reactions of sulfur→PATTERNS—NON-METALSAs a dehydrating agentCH3CH2OHC12H22O11CuSO4 .5H2OH2SO4170 °CH2SO4–11H2OH2SO4–5H2OCH2 = CH212CCuSO491The halogens: group 7PATTERNS—NON-METALSKey words1 Electron structureF27Cl8721878187BrI2inner electronsastatinebrominechlorinecovalent bondcovalentcompoundfluorinehalogensiodineionic compoundHalogens● Theelements of group 7 aresometimes referred to as the halogen s.They are flou rin e, chlorin e, brom in e,iodin e, and astatin e.
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