Edexcel A Level Chemistry Practicals Questions And Answers 100% Guaranteed Success.

Edexcel A Level Chemistry Practicals Questions And Answers 100% Guaranteed Success. 1)a. fMeasure fthe fmolar fvolume fof fa fgas f(topic f5.2) f- fcorrect fanswers. foverall fequation: fCaCO3 f+ f2CH3COOH f-- fCa(CH3COO)2 f+ fCO2 f+ fH20 Measure fthe fgas fevolved fthrough fan finverted fcylinder for fwith fa fgas fsyringe. f A fweak facid fis fused fto fmake fthe freaction fslower fso fless fgas fis flost fat fa ftime 1)b. fMeasure fthe fmolar fvolume fof fa fgas- fpurpose fand ferrors f- fcorrect fanswers. ftrying fto fprove fAvogadro's flaw: fThe fmolar fvolume fof fany fgas fat fSTP f(298K fand f1atm/101 fkPa) fis f= f24dm^3 Errors: f Gas floss fdue fto fbung fnot fbeing fair ftight, for fsome fescapes fwhen fthe fmarble fchips fare fadded. f CO2 fis fslightly fsoluble fin fwater fso fexact fvolume fis funknown. f Weighing fby fdifference fensures fexact famount fof fCaCO3 fadded fis fknown. 2)a. fprepare fa fstandard fsolution fof fa fsolid facid fsalt f(topic f5.3) 3)a. fprepare fa fstandard fsolution fof fNaOH f(same fapplies fjust fdifferent fsalt) f- fcorrect fanswers. fOutline fof fmethod: fweight fby fdifference fsolid facid. f Dissolve fin fdeionized fwater. Transfer fto fa fvolumetric fflask fand ffill fto fmark. fDon't fforget fto fadd fwashings. Invert fto fmix key fpoints: f acid fmust fhave fhigh fmolar fmass fto freduce fweighing ferrors. sample fmust fbe fpure fand fnot fair fsensitive 2)b. ftitrate fthe facid fsolution fagainst fNaOH fto ffind fthe fconcentration fof fNaOH 3)b. ftitrate fthe fstandardised fNaOH fagainst fHCL fto ffind fthe funknown fconcentration fof fthe fHCL f(same fapplies fjust fused fphenolphthalein fas findicator fand fhave fNaOH fin fthe fburette) f- fcorrect fanswers. fOutline fof fmethod: Clean fapparatus fwith fdeionized fwater fand fa flittle fbit fof fthe ftitrate fto fcover fthe fburette fand fanalyte fto fcover fpipette fto freduce fdilution. f Pipette fan faliquot fof fthe fanalyte finto fa fconical fflask. fAdd findicator. f Titrate funtil fconcordant fresults fare freached. f In fcalculations fuse fmean ftitre. 2)c. ffind fthe fconcentration fof fNaOH- ftitration ferrors 3)c. ffind fthe fconcentration fof fHCL- ftitration ferrors f- fcorrect fanswers. fSwirl fthe fflask fbetween faddition fto fensure fit fmixes fproperly. f use fa fwhite ftile fto fmake fcolour fchange fclearer Wash fdown fthe fwalls fof fthe fflask fwith fdistilled fwater fto fmake fsure fall fof fthe ftitrant freacts fwith fthe fanalyte. f Read fthe fbottom fof fthe fmeniscus fat feye flevel f(reduce fparallax ferror). f Calibrate fpipette fby fensure fthere fare fno fair fbubbles. If fphenolphthalein fis fused, fthe freaction fmixture fwill fturn fgo fcolourless fif fleft fto fstand/swirled. fAs fNaOH freacts fwith fCO2 fin fthe fair. fSo fif fpink fcolour fpersists ffor f5 fseconds- fend fpoint fhas fbeen freached 4)a. finvestigate fthe fhydrolysis fof fhalogenoalkanes- fmethod f- fcorrect fanswers. fSet fup f3 ftest ftubes fof fethanol fand ftwo fdrops fof fthe fdifferent fhaloalkanes fin fthe fseparate ftest ftubes. Place fthem fin fa fwater fbath f(50-60 fdegrees fcentigrade) fwith fa fseparate ftest ftube fof fsilver fnitrate. fLeave fthem funtil fthey fall freach fthe fsame ftemp. f Quickly fadd fsilver fnitrate finto feach ftest ftube f(equal famounts fas fethanol) fand fstart fa fstopwatch. f Measure fand frecord fthe ftime ftaken ffor fthe fppts fto fform. f Do fthis ffor fprimary, fsecondary fand ftertiary fhaloalkanes. 4)b. fhydrolysis fof fhaloalkanes- fresults fand ferrors f- fcorrect fanswers. fThis fis fnucleophilic fsubstitution: RX f+ fH2O f-- fROH f+ fH+ f+ fX- X- f+ fAg+ f-- fAgX(s) AgCl f= fcolourless f(ppt ftakes ftoo flong fto fform) AgBr= fcream AgI= fyellow fthick fppt Chloro(slowest)--Iodo(fastest) Primary(slowest)--tertiary(fastest) Errors- f water fbath fcontrols ftemp. f lower ftemp freduces frate fof freaction. fSo ftime fis flonger ftherefore flower funcertainty. 5)a. fPartial fand fcomplete foxidation fof fprimary falcohols fmethod f- fcorrect fanswers. fComplete foxidation: f Add facidified fpotassium fdichromate(VI) fsolution finto fthe fpear fshaped fflask. fand fcool fin fan fice fbath. f Add fa ffew fanti-bumping fgranules fto freduce fthe fformation fof flarge fgas fbubbles fthat fcause fviolent fboiling. f Add fthe falcohol fdrop fwise finto fthe fpear-shaped fflask fand fstir. fAllow fthe fmixture fto fwarm fto froom ftemp. Step fup freflux fapparatus, fand fheat fthe fflask. fColour fshould fchange ffrom forange fto fgreen. fAllow fto fcool fand fset fup fthe fdistillation fapparatus fto fcollect fthe fproduct. Partial fOxidation: f Repeat fas fabove fbut fdistill fthe freaction fmixture fnot freflux fto fproduce fthe faldehyde. 5)b. foxidation fof fprimary falcohols- ftesting fproducts f- fcorrect fanswers. fSee fif fit freacts fwith facid. fIf feffervescence fis fseen fthen fa fcarboxylic facid fhas fbeen fmade. f Use ffehling's fsolution, fif fit fforms fa fbrick fred fppt fthen fan faldehyde fhas fformed. 6)a. fChlorination fof f2-methylpropan-2-ol fmethod f- fcorrect fanswers. fOverall fequation: f(CH3)3COH f+ fHCL(conc.) f-- f(CH3)3CCL f+ fH2O Add fconcentrated fHCL fto fthe ftertiary falcohol fto fa fconical fflask. f Add fa fbung fand fswirl fgently, frelease fthe fpressure ffrom fthe fgas fproduced ffrom ftime fto ftime. fRepeat fthis fregularly ffor f20 fminutes. Add fsome fanhydrous fCaCl2 fand fswirl. fTwo fdistinct flayers fshould fform. fTransfer fto fseparating ffunnel fand fdiscard fbottom faqueous flayer. f Add fNaHC03 fsolution fto fthe forganic flayer fto freact fwith fany fremaining fHCL. fInvert fthe ffunnel fand frelease fthe fpressure fbuild fup fa ffew ftimes. Run foff fthe fnew faqueous flayer. fAnd ftransfer fthe forganic flayer finto fa fclear fflask. fAdd fsome fanhydrous fNa2SO4 fto fdry fthe fmixture. fSwirl fit fand fleave fto fstand funtil fcompletely fclear. f Decant fthe fliquid finto fa fpear-shaped fflask fand fdistill fthe fproduct fto fpurify. fcollect fthe ffraction fbetween f50-52 fdegrees fcentigrade. Errors- fsome fproduct fis flost fwhen ftranferring fbetween fvessels 8) fEnthalpy fchange ffor fdecomposition fof fKHCO3- fmethod f- fcorrect fanswers. fcannot fbe fmeasured fdirectly fas fheating fis frequired fso fchange fin ftemp fis fnot fexclusive fto fthe fKHCO3 So ftwo freactions fwith fmeasurable fenthalpy fchanges fare fcombined. f Hess's flaw: fthe fenthalpy fchange ffor fa freaction fis findependent fto fof fthe fpath ftaken. f Record fthe ftemp fof fone fof fthe freactants fin fthe fcup fevery fminute fupon faddition. fAt f4 fminutes fadd fthe fsecond freactant. fDon't fstart frecording fthe ftemp ftill f5 fminutes fand fthen frecord fthe ftemps fevery fminute fafter fthat ffor f10 fmins. f plot fa fgraph fand fextrapolate fto ffind fchange fin ftemp. 8)b. fmeasure fenthalpy fchange fof fdecomposition fof fKHCO3- fkey fpoints fand ferrors f- fcorrect fanswers. fThis fpractical fcombines ftwo fneutralisation freactions: f 1. fK2CO3 f+ f2HCL f-- f2KCL f+ fH2O f+CO2 2. f2KHCO3 f+ f2HCL f-- f2KCL f+2H20 f+2CO2 f The fdesired freaction fis: 2KHCO3 f-- f2K2CO3 f+CO2+ fH2O use fQ=mcΔT fand fΔH=-Q/n Errors- fassume fspecific fheat fcapacity fis fthe fsame fas fwater. fHeat flost fto fsurroundings. fPolystyrene fis fmore finsulating fthan fglass fso fthis fcan freduce fthe fheat flost 9)a ffinding fKa ffor fa fweak facid- fmethod f- fcorrect fanswers. fmethod- 1 ftitrate f25cm^3 fof fthe facid fbeing ftested fagain fNaOH. fUse fphenolphthalein findicator. 2 fAfter ftitration, fadd fanother f25cm^3 fof facid finto fthe fsame fflask. fThis fis fequal fto fhalf-equivalence fpoint. 3 fUse fpH fmeter fto fmeasure fpH fof fsolution. fThe fpH f= fpKa f(since fhalf-equivalence fpoint). fKa f= f10^pKa 9)b ffinding fKa ffor fa fweak facid- fusing fa fpH fmeter fand ferrors f- fcorrect fanswers. fcalibrate fwith fdeionised fwater fand fbuffer fsolutions fof fknow fpH. Wash fin fbetween freadings fto fremove fions. Are fgood fbc: fread fto f2 fd.p fand funlike findicators fit fdoesn't fadd for fremove fions. errors- burette freadings, fover-shooting fend fpoint f(subjective fdecision) 10)a finvestigation fof fsome felectrochemical fcells- fmethods f- fcorrect fanswers. f1 fFor feach fhalf fcell, fclean felectrodes fwith fsandpaper. 2 ffor fsalt fbridge: fsoak fstrip fof ffilter fpaper fin fKNO3 f( fuse fk+ fand fNO3- fas fare fsoluable fsalts fso fprevent fppt fforming) 3 fconnect fcircuit fto fhigh fresistance fvoltmeter 10)b finvestigation fof fsome felectrochemical fcells- fkey fpoints fand fsafety f- fcorrect fanswers. fkey fpoints: f standard fconditions- f1moldm^-3, f100kPa, f298 fK for fthermodynamically ffeadible fprocess fEMF fhas fto fbe fpositive. fWhere fEMF f= fEright(reduction)-Eleft(oxidation) safety: f some ftoo fdangeroid fat f1moldm^-3 f(e.g. fsilver fnitrate fis fhighly foxidising). ZnSO4 fand fFeSO4 fneed fto fbe fdisposed fof fsafely fas fharmful fto fenvironment. Electrodes fmade fof finert fsubstance. Differences fbetween fexperimental fand ftheoretical fvalues farise ffrom fconditions fnot fbeing fstandard 11)a fRedox ftitration:Find fpercentage fof firon fin ftablet- fprepare firon f(II) fsolution f- fcorrect fanswers. f1 fUse fmortar fand fpestle ffor fcrushing fthe ftablets fto fa fpowder. fWeigh fby fthe fdifference fin fmass fto fhave fan fidea ffor fhow fmany fgrams fof fpowder fis fbeing fadded 2 fadd fH2SO4 fand fstir fto fdissolve f 3 ffilter fsolution finto fa fvolumetric fflask fto fremove fany fundissolved fsolids f 4 fWash fbeaker fand fthe ffilter fpaper fwith fdistilled fwater fto fget fremaining fsolution finto fthe fvolumetric fflask. f 5 fDilute fthe fsolution fin fthe fvolumetric fflask fby fadding fsulphuric facid fto fthe f250cm^3 fmark. 11)b fRedox ftitration:Find fpercentage fof firon fin ftablet- ftitration f- fcorrect fanswers. f1 fPrepare fthe ftitration fequipment. fAdd fKMnO4 fto fburette f(use fburette fwith fwhite fmarkings fas fsolution fis fdeep fpurple) 2 fAdd fknown fvolume fof firon fsolution fto fconical fflask. fNo findicator fis fneeded fas fKMnO4 fis fself findicating. fEnd fpoint fis fwhen fyou ffirst fsee fa fpermanent fpale fpink fcolour. 3 fTitrate fsolution fand frepeat funtil fyou fget fconcordant ftitres. fCalculate fmean ffrom fconcordant ftitres. 11)c fRedox ftitration:Find fpercentage fof firon fin ftablet- fcalculations fand ferrors f- fcorrect fanswers. fionic fequation: 5Fe2+ f+ fMnO4- f+ f8H+ f-- f5Fe3+ f+ fMn2+ f+ f4H2O From fresults fcalculate fmoles fof fMnO4-. f1:5 fratio fso fmoles fof fFe2+ f= f5 fx fmoles fof fMnO4-. Multiply fby f10 fto ffind fmoles fof fFe2+ fin f250cm^3. Rearrange fn=n/M f-- fm= fn fx fM. fThis fgives fthe fmass fof fFe fin fthe ftablet. fCompare fto fvalue fon fbox. f Errors: fensure fas fmuch fof fthe fpowder fis fadded fand fdissolved, fwarming fmay fhelp. fAdd fin fwashings ffrom fthe fcontainers fto fget fas fmuch firon fas fpossible. fUse fa fwhite ftile fto fsee fthe fend fpoint fclearly. 12)a fprepare fa ftransition fmetal fcomplex- fmethod f- fcorrect fanswers. f1 fWeigh fout fthe fmass fof fcopper fsulphate faccurately fand fdissolve fin fdistilled fwater f(can fweigh fby fdifference). 2 fIn ffume fcupboard fadd fconc fammonia. f 3 fStir fthe fmixture fand fpour finto fethanol. fThen, fcool fthe fmixture fin fice fbaths. fCrystals fwill fform. f 4 fSet fup fvacuum ffiltration fapparatus fwith fbuchner ffunnel. fCollect fthe fcrystals fin fthe ffunnel. fWash ftube fwith fcold fethanol fand ffilter fagain, fthen fwash fthe fcrystals fwith fcold fethanol. f 5 fLeave fcrystals fon ffunnel fto fdry. fThen fuse ftwo ffilter fpapers fto fdry fcrystals feven fmore. 6 frecord fmass fand fwork fout fpercentage fyield f(relative fto fthe fhydrated fcopper fsulphate) 12)b fprepare fa ftransition fmetal fcomplex- fsafety fand ferrors f- fcorrect fanswers. fhydrated fcopper fsulphate fis fharmful fto faquatic flife, fso fuse fsmall fquantities. f