CALCULATIONS Gas Difussion

8/18/2019 CALCULATIONS Gas Difussion

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* - effective distance of mass transfer /m0

T - total molar concentration

kmol

m3

¿0

BM - logarithmic mean value of B /

kmol

m3 0

1vaporation of the liquid ,

!’A -( ρ L

M )dL

dt %B'

Where " p* - density of liquid /kg

m3 ¿

M - molecular eight /kg

kmol 0

ombination of equation A and B ,

% ρ L

M ¿

dL

dt - ( %C A

L ' %C T

C BM '

The *2 is at t - 2" the slope of plotting the graph oft

L− L0

against % * # *2 ',

3 - % ρ L

2 MD ' %

C BM

C AC T

'

The diffusivity ,


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( -

ρ LC BM

2 MC AC T s


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4.0 DIAGRAM AND DESCRIPTION OF APPARATUS

The 34*T15 6aseous (iffusion oefficient Apparatus consists of ater bath tank" capillary

tube" air pump and travelling telescope. 7n ater bath tank" there are some additional parts that

help this experiment orks such as heater W8" temperature sensor" temperature controller and

level sitch. The purpose of heater W8 is to heat up the ater in the ater bath to the

temperature desired. Temperature sensor is to measure the temperature by correlating the

resistance of the element ith the temperature. Temperature controller is about controlling the

temperature folloing the experimental temperature and ater bath itself can maintain a steady

temperature so that there is no eddy current in the vertical tube and mass transfer takes place

from the surface by molecular diffusion alone. !ext" the T9shape vertical capillary tube is used

ith the air pump hich has been attached to the one end of the T9Tube. The purpose is to allo

the maintenance of a partial pressure difference ithin the capillary tube beteen the evaporating

liquid surface and the floing air stream. The travelling telescope equipped ith a vernier scale

is used to measure the level of the acetone meniscus ithin the capillary


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)76:;1 8


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RESULTS

Temperature = 50 ℃

Lo=9mm

Time (ks) Time from

commencem

ent of

experiment, t

(min)

Liquid level (

L− LO )

(mm)

t/( L− LO )

(ks/mm)

Reading of

vernier, L

(mm)

000 000 000 000 000!"0 "00 !50 0#0 !05"$0 $00 %50 0&' !"5%&0 &00 500 0" !$0$#0 #00 #$0 05 !$&00 !00 !0& 05 !'&"0 !"0 !"0 0&0 "!0

CALCULATIONS

olecular *eig+t, = 5#0# kg/mol

Temperature, T a = 50 ℃ = %"%

-ressure, Pa = !0!% k./m

mol volume = ""$ m

ensit1, ρ L = '! kg/m

2apour pressure, Pv = 5& n/m3


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4solute temperature,|¿|T ¿ = "%

T |¿|

T a¿

C T =( 1 Kmol volume )¿

¿( 122.4mᶾ )( 273 K 323 K )=0.03773 kmol /mᶾ

Logarit+mic mean molecular concentration of vapour, C BM (kmol/m)

C B1=C T

C B1=0.03773 kmol /mᶾ

C B2=( Pa− Pv

Pa

)C T

C B2=( 101.3kN /m²−56kN /m²101.3kN /m ² )0.03773 kmolmᶾ =0.01687 kmolmᶾ

C BM =(C B1−C B2)

ln

(C B1

C B2

)

=(0.03773

kmol

mᶾ −0.01687

kmol

mᶾ )

ln

(0.03773kmol /mᶾ

0.01687 kmolmᶾ )

=0.02592kmol

mᶾ

6aturation concentration at interp+ase, C A kmol/mᶾ


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C A=( P v P a )C T

C A=( 56kN /m²101.3 kN /m² )

0.03773kmol

mᶾ =0.002086

kmol

mᶾ

Graph of t versus liquid level

0 " $ & # !0 !" !$0

0!

0"

0%

0$

05

0&

0

0#

0'

Liquid level (L-Lo) ()

t!( L-Lo) ("s!)


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#ISCUSSION $

T+is experiment *as conducted to otain t+e gas di7usion

coe8cient of acetone using t+e 9inkelmann:s met+od ;n t+is experiment,t+e volatile liquid is +eated until it evaporated into free air stream T+e rateof di7usion can e oserved 1 t+e rate of decreasing of acetone level in t+etue 1 using a telescope i7usion is t+e movement of molecules from areaof +ig+ concentration to area of lo*er concentration and t+is is increased*it+ increasing temperature *+ic+ means *+en t+e temperature increaset+e di7usion *ill also rising up ;n t+e ot+er *ord, *+en temperature is+ig+er, t+en t+e rate of di7usion *ould proal1 increase caused 1increasing kinetic activit1 of t+e solution

axis of t+e grap+ is t+e time taken divide 1 t+e di7erenceet*een t+e levels of acetone ;n addition, t+e trend of t+e grap+ isincreased proportionall1 T+e increasing t+e di7erence et*een t+e levels of

acetone, t+e increasing t+e time divide 1 t+e di7erence et*een t+e levelsof t+e acetone rom t+e calculation and t+e data from t+e tale, t+e value of di7usivit1 *as determined *+ic+ is %$$ m"/s

T+e temperature controller *as set up at 50@A t+roug+ along t+eexperiment and it not een set e1ond 0@A ;t is ecause t+e oiling pointof t+e acetone is at 5&@A *+ere t+e process *+ere t+e p+ase of acetone


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c+ange from liquid to vapor 9+en t+e temperature exceeds 0@A, t+e rate of evaporation is faster compare to temperature at t+e oiling point T+issituation can cause t+e prolem to t+e experimenter to collect t+e data ordi7erence of acetone level inall1, t+e discrepanc1 from t+e experimentaldata is t+e value of t+e time divide 1 di7erence et*een levels of acetoneet*een intervals is not increased constantl1 due to some errors suc+ asparallax error and t+e initial value of t+e acetone in t+e capillar1 tue *asnot read accuratel1

CALCULATIONS Gas Difussion

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