CHEMICAL ENGINEERING QUESTIONS
AND SOLUTIONS
Describe fthe fdifference fbetween fChemists fand fChemical fEngineers f- fans-
Chemists fare fon fa fsmaller fscale, fdo fmore fresearch, fare finnovative, fdocument
freactions, fand fdevelop fnew fcompounds. fChemical fEngineers fwork fwith
fexisting fmaterials, fare fon fa flarger fscale, fand ffocus fon fstorage/transport fand
fplant fdesign/operation. fBoth ftake fchemistry, fbust fchemists ftake fmore fdetailed
fcourses.
What fis fChemistry? f- fans-The fscientific fstudy fof fmaterials, ftheir fcomposition
fand fstructure, fproperties, finteractions, fand fchanges fthey fundergo.
What fare fThermodynamics? f- fans-The fstudy fof fwork, fenergy, fand fefficiency fin
flarge-scale fsystems.
Zeroth fLaw f- fans-Thermal fEquilibrium
First fLaw f- fans-Law fof fconservation fof fenergy
Second fLaw f- fans-Energy fwill fnaturally fdisperse
Entropy f- fans-The ftendency fof fall fenergy fand fmatter fto fseek fa fstate fof
funiformity
Third fLaw f- fans-The fcolder fa fsubstance fgets, fthe fless fits fatoms fmove
What fare fFluid fDynamics? f- fans-Study fof ffluid fflow
Turbulent fFlow f- fans-Velocity ffluctuations; fhighly fdisordered
Contains fswirls fof fwater fcalled f"eddies"
Fluid fparticles fflow fin fmany fdirections fwith fno fobservable fpaths
As fturbulent fflow fincreases, fso fdoes fenergy fneeded fto fmove fit
Inertial fforces fdominate
Laminar fFlow f- fans-Has fno fdisruption fbetween flayers fof ffluid
Smooth fstreamlines, fhighly fordered
Little fto fno fmixing; fparticles fflow fin fa fstraight fpath
Viscous fforces fdominate
What fis fFluid fFlow fcharacterized fby? f- fans-Reynolds fNumber
, RN f= fDensity fx fVelocity fx fDiameter fof fPipe f/ fDynamic fViscosity
Under f2,500 f=> fLaminar
Over f10,000 f=> fTurbulence
Mass fBalance f- fans-States fthat fmatter fcannot fbe fcreated for fdestroyed fand
fmust fbe fconstant fin fa fclosed floop.
Amount fof fmaterial fthat fexists fprior fto fchemical freaction fis fequal fto fthe
famount fof fmaterial fafter fthe freaction.
Differential fMass fBalance f- fans-Measurement ftaken fat fthe fsame fpoint fover
ftime.
Applied fto fa fcontinuous fprocess.
Should falways fbe fthe fsame.
Each fterm fin fa fdifferential fbalance fequation frepresents fa fprocess fstream fand
fthe fmass fflow frate fof fthe fchemical(s) fin fthat fstream.
Integral fMass fBalance f- fans-Are ftaken fat f2 fdifferent fpoints fto fshow fwhat fis
fhappening fbetween f1 fpoint fand fanother.
Typically ftaken fat fbeginning fand fend fof fprocess.
Each fterm fin fan fintegral fbalance frepresents fa fprocess fstream fand fthe fmass
fof fthe fchemical(s) fin fthat fstream.
Fluid fFlow fRate, fPressure, fand fTemperature f- fans-What fare fcrucial fto
fmeasure?
Differential fPressure fFlowmeter f- fans-Relies fon fthe fconcept fthat fas fspeed fof
fa ffluid fincreases, fits fpressure fdecreases.
Constrict fthe fflow fusing fan fobstruction for fnarrowing fof fthe fpipe.
Flow fRate f= fPressure fat fobstruction fvs fPressure faway ffrom fobstruction
Velocity fFlowmeter f- fans-Measure fthe fspeed fof fpassing ffluid fand fthe fdepth.
Used fin fairplanes fto fmeasure fspeed frelative fto fthe fair.
Mechanical fFlowmeter f- fans-Uses fa fvariety fof fmechanical fdevices finside fpipe.
Impeller f- fans-Measures fthe fnumber fof frotations fper funit ftime
Mass fFlowmeter f- fans-Measure fmass frather fthan fvolume.
Used fwhen fmeasuring fgases.
Open-Channel fFlowmeter f- fans-Measure fflow fin fa fchannel frather fthan fin fa
fpipe, fas fin fa fstream for fa friver.
Measured fby fforce fper funit farea f- fans-How fis fpressure fmeasured?
Gauge fPressure f- fans-Relative fto fatmospheric fpressure.
AND SOLUTIONS
Describe fthe fdifference fbetween fChemists fand fChemical fEngineers f- fans-
Chemists fare fon fa fsmaller fscale, fdo fmore fresearch, fare finnovative, fdocument
freactions, fand fdevelop fnew fcompounds. fChemical fEngineers fwork fwith
fexisting fmaterials, fare fon fa flarger fscale, fand ffocus fon fstorage/transport fand
fplant fdesign/operation. fBoth ftake fchemistry, fbust fchemists ftake fmore fdetailed
fcourses.
What fis fChemistry? f- fans-The fscientific fstudy fof fmaterials, ftheir fcomposition
fand fstructure, fproperties, finteractions, fand fchanges fthey fundergo.
What fare fThermodynamics? f- fans-The fstudy fof fwork, fenergy, fand fefficiency fin
flarge-scale fsystems.
Zeroth fLaw f- fans-Thermal fEquilibrium
First fLaw f- fans-Law fof fconservation fof fenergy
Second fLaw f- fans-Energy fwill fnaturally fdisperse
Entropy f- fans-The ftendency fof fall fenergy fand fmatter fto fseek fa fstate fof
funiformity
Third fLaw f- fans-The fcolder fa fsubstance fgets, fthe fless fits fatoms fmove
What fare fFluid fDynamics? f- fans-Study fof ffluid fflow
Turbulent fFlow f- fans-Velocity ffluctuations; fhighly fdisordered
Contains fswirls fof fwater fcalled f"eddies"
Fluid fparticles fflow fin fmany fdirections fwith fno fobservable fpaths
As fturbulent fflow fincreases, fso fdoes fenergy fneeded fto fmove fit
Inertial fforces fdominate
Laminar fFlow f- fans-Has fno fdisruption fbetween flayers fof ffluid
Smooth fstreamlines, fhighly fordered
Little fto fno fmixing; fparticles fflow fin fa fstraight fpath
Viscous fforces fdominate
What fis fFluid fFlow fcharacterized fby? f- fans-Reynolds fNumber
, RN f= fDensity fx fVelocity fx fDiameter fof fPipe f/ fDynamic fViscosity
Under f2,500 f=> fLaminar
Over f10,000 f=> fTurbulence
Mass fBalance f- fans-States fthat fmatter fcannot fbe fcreated for fdestroyed fand
fmust fbe fconstant fin fa fclosed floop.
Amount fof fmaterial fthat fexists fprior fto fchemical freaction fis fequal fto fthe
famount fof fmaterial fafter fthe freaction.
Differential fMass fBalance f- fans-Measurement ftaken fat fthe fsame fpoint fover
ftime.
Applied fto fa fcontinuous fprocess.
Should falways fbe fthe fsame.
Each fterm fin fa fdifferential fbalance fequation frepresents fa fprocess fstream fand
fthe fmass fflow frate fof fthe fchemical(s) fin fthat fstream.
Integral fMass fBalance f- fans-Are ftaken fat f2 fdifferent fpoints fto fshow fwhat fis
fhappening fbetween f1 fpoint fand fanother.
Typically ftaken fat fbeginning fand fend fof fprocess.
Each fterm fin fan fintegral fbalance frepresents fa fprocess fstream fand fthe fmass
fof fthe fchemical(s) fin fthat fstream.
Fluid fFlow fRate, fPressure, fand fTemperature f- fans-What fare fcrucial fto
fmeasure?
Differential fPressure fFlowmeter f- fans-Relies fon fthe fconcept fthat fas fspeed fof
fa ffluid fincreases, fits fpressure fdecreases.
Constrict fthe fflow fusing fan fobstruction for fnarrowing fof fthe fpipe.
Flow fRate f= fPressure fat fobstruction fvs fPressure faway ffrom fobstruction
Velocity fFlowmeter f- fans-Measure fthe fspeed fof fpassing ffluid fand fthe fdepth.
Used fin fairplanes fto fmeasure fspeed frelative fto fthe fair.
Mechanical fFlowmeter f- fans-Uses fa fvariety fof fmechanical fdevices finside fpipe.
Impeller f- fans-Measures fthe fnumber fof frotations fper funit ftime
Mass fFlowmeter f- fans-Measure fmass frather fthan fvolume.
Used fwhen fmeasuring fgases.
Open-Channel fFlowmeter f- fans-Measure fflow fin fa fchannel frather fthan fin fa
fpipe, fas fin fa fstream for fa friver.
Measured fby fforce fper funit farea f- fans-How fis fpressure fmeasured?
Gauge fPressure f- fans-Relative fto fatmospheric fpressure.
