phy chem experiment 3

8/18/2019 Phy Chem Experiment 3

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Determination Of Absolute Viscosity Using Ostwald Viscometer By Wenddie Aquien from The Handbook of Research on Virtual Workplaces and the New Nature of

Business Practices. Eds. Kirk t. Amant and !a"el #emlansky. $ers%ey& !A' (dea )rou* !ublis%ing&

+,,-.

Abstract: %e e/*eriment 0Determination of absolute "iscosity using Ostwald Viscometer1

was conducted to determine t%e absolute "iscosity of organic liquids& t%e relations%i* of "iscosity to tem*erature of sucrose solution and t%e unknown concentration of sucrose

solution using Ostwald "iscometer. A definite "olume of liquid is *laced in t%e "iscometer&

and t%e le"el of t%e liquid is drawn abo"e t%e to* mark of t%e bulb by suction. %e liquid is

allowed to flow out freely& and t%e time& t& required for t%e le"el to dro* from t%e u**er mark to t%e lower mark is measured. West*%al balance is also used in t%is e/*eriment in measuring

t%e density of t%e liquid. %e e/*eriment concluded t%at t%e "iscosity of a sim*le liquid

decreases wit% t%e increasing tem*erature and "ice "ersa. As tem*erature increases& t%ea"erage s*eed of t%e molecules in a liquid increases and t%e amount of time t%ey s*end in

contact wit% t%eir nearest neig%bors decreases. %us& as tem*erature increases& t%e a"erageintermolecular forces decrease.

Keywords' Viscosity& Ostwald Viscometer& West*%al Balance

I. INTRODUCTION

%e internal friction in fluids& or "iscosity& is caused by t%e co%esion forces between

molecules. 2olecules need energy to esca*e from eac% ot%er3s close interactions. Viscosity is

t%erefore a t%ermodynamic quantity& de*endent on tem*erature and *ressure. 4urt%ermore&

"iscosity is a measure of t%e resistance of a fluid to being deformed by eit%er s%ear stress or

e/tensional stress. (t is commonly *ercei"ed as 0t%ickness1& or resistance to flow. Viscosity

describes a fluid3s internal resistance to flow and may be t%oug%t of as a measure of fluid

friction. %ere are actually two quantities t%at are called "iscosity. %e quantity defined

abo"e is sometimes called dynamic "iscosity& absolute "iscosity& or sim*le "iscosity to

distinguis% it from t%e ot%er quantity& but is usually 5ust called "iscosity. %e ot%er quantity

called kinematic "iscosity 6re*resented by t%e symbol 7 0nu18 is t%e ratio of t%e "iscosity of a

fluid to its density 62ott& 9. :. +,,;8


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Viscosity %as a unit of *oise in cgs w%ic% is named after t%e 4renc% *%ysician ?? @ =-;?8. !oise is equi"alent to dynesecond *er square

centimeter. (t is t%e "iscosity of a fluid in w%ic% a tangential force of = dyne *er square

centimeter maintains a difference in "elocity of = centimeter *er second between two *arallel

*lanes = centimeter a*art.

=

+

$a"ing known t%e "iscosity of a liquid is im*ortant. %us& "iscosity *lays a "ital role

to our daily li"es. (n t%e medical field for e/am*le& doctors always measures %ow "iscose t%e

blood of %is *atient is. (t is because w%en a *atient3s blood is too t%ick t%en it can cause

clotting and lead to a %eart attack or stroke& or if it3s too t%in t%en %e can readily bleed from a

small cut for %ours. On t%e ot%er %and& in t%e %emical Engineering field& "iscosity

measurement also *lays a big *art in t%e industry.

4or e/am*le& w%en an engineer designs for t%e distribution system of water from a

water *lant for a town& gi"en t%e a"erage demand of water for t%e town for any gi"en time&

knowing t%e "iscosity of water& engineers will be able to know t%e flow of t%e water& t%e

*ressure of t%e *i*es underground& t%e siCe of *i*es to be used& and more to follows.


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(n t%e e/*eriment& t%e "iscosity of two liquids can be com*ared by making use of an

Ostwald. %e liquids are allowed to flow t%roug% t%e ca*illary w%ile timed to determine

e/*erimental "iscosity of eac% of t%e liquids being test.

(n doing t%e e/*eriment& it is im*ortant t%at t%e students know before%and t%e basic

*rinci*le t%at t%e density is t%e main factor t%at brings about t%e differences in t%e "iscosity

of t%e different liquids. %us& density is directly *ro*ortional to t%e "iscosity& t%erefore& t%e

smaller t%e density of a liquid& t%e smaller t%e smaller t%e "iscosity is& or "ice "ersa. Also&

"iscosity "aries wit% tem*erature. (n general& t%e "iscosity of a sim*le liquid decreases wit%

increasing tem*erature 6and "ice "ersa8. As tem*erature increases& t%e a"erage s*eed of t%e

molecules in a liquid increases and t%e amount of time t%ey s*end 0in contact1 wit% t%eir

nearest neig%bors decreases. %us& as tem*erature increases& t%e a"erage intermolecular

forces decrease. %e e/act manner in w%ic% t%e two quantities "ary is nonlinear and c%anges

suddenly w%en t%e liquid c%anges *%ase. Viscosity is normally inde*endent of *ressure& t%is

do not "aries t%e "alue of "iscosity. ince liquids are normally incom*ressible& an increase in

*ressure doesn3t really bring t%e molecules significantly closer toget%er.

:astly& different fluids *ossess different amounts of "iscosity' syru* is more "iscous

t%an water grease is more "iscous t%an t%e engine oil liquids in general are muc% more

"iscous t%an gases. %e "iscosity of different fluids can be e/*ressed quantitati"ely by t%e

coefficient of "iscosity& F 6t%e )reek lowercase letter eta8& w%ic% could be defined and

calculated using t%e data t%at gat%ered in t%e following e/*eriment


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G

Chapter 2

DESIGN AND METHODOLOGY

%e e/*eriment was *erformed using t%e Ostwald "iscometer . A clean Ostwald

"iscometer was used in order to attain t%e acquired "alue for t%e e/*eriment. %e

atmos*%eric *ressure was measured using t%e barometer and was essential to t%e data

acquired for t%e entirety of e/*eriment. %ermometer is used to measure t%e tem*erature of

t%e liquid. A West*%al balance was used to measure t%e density of t%e water& benCene&

c%loroform& met%anol and t%e unknown liquid. to*watc% was used in measuring t%e time

t%at t%e liquid *ass t%roug% t%e reading mark in t%e "iscometer. ime& *ressure& density was

found utiliCing t%e !ouiselle3s equation.


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Before starting t%e e/*eriment& t%e re*orters followed t%e O! and guidelines for t%e

laboratory 6wearing t%eir lab gowns& et al8. to start t%e e/*eriment& a clean Ostwald

"iscometer was was%ed wit% %ydroc%loric acid followed by distilled water in order to was%

all t%e remains of t%e ot%er liquid t%at stayed in t%e "iscometer. After t%e was%ing comes t%e

drying. %e "iscometer is clam*ed "ertical using t%e clam* and t%e iron stand in order to read

t%e "alue or t%e time ela*sed. Hml of water was *ut into t%e "iscometer in arm using t%e

*i*ette until it is abo"e t%e mark at t%e to* of t%e bulb. !ut t%e rubber in t%e ot%er arm of t%e

"iscometer in order to draw u*ward t%e water. Draw t%e water u* t%e ot%er arm of t%e tube

until it is abo"e mark A. using t%e sto*watc%& time t%e water as t%e surface falls between

mark A and B. 9e*eat twice more and take t%e a"erage reading of t%e t%ree as your mean

time.

After t%e t%ree trials for water& em*ty t%e "iscometer on t%e sink wit% *lenty of water.

I

H

9e*eat t%e *rocedure wit% benCene& c%loroform followed by met%anol t%en t%e

unknown liquid. After t%e t%ree trials for c%loroform& trials of t%e same number for

benCene &met%anol and unknown liquid were made. 9esults t%at followed were recorded.

am*le com*utations were made and *assed after t%e +day of t%e designated E/*eriment .


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Chapter 3

RESULTS AND DISCUSSION

%roug%out t%e course of t%e e/*eriment& t%ree trials were *erformed for eac% of t%e

com*ounds 6water& benCene& c%loroform& met%anol and an unknown reagent8 for t%e

determination of absolute "iscosity using t%e Ostwald "iscometer. %e Ostwald "iscometer

was used to measure t%e "iscosity of eac% of t%e fluids in t%e e/*eriment. %e drag caused

by t%e relati"e motion of t%e fluid and a surface is a measure of t%e "iscosity. %e flow

conditions must %a"e a sufficiently small "alue of 9eynolds number for t%ere to be a laminar

flow. Density is also *art of t%e equation of determining t%e "iscosity of t%e fluids& t%erefore

t%e *erformers of t%e e/*eriment did t%ree trials for eac% of t%e reagents of t%e e/*eriment


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using t%e West*%al balance. %e tem*erature at t%e gi"en density was also measured

because it is one of t%e factors in t%e density of t%e reagents. 4or t%e e/*erimentJs *rocess

"ariable& "iscosity of a fluid is a measure of its resistance to gradual deformation by s%ear

stress or tensile stress. 4or liquids& it corres*onds to t%e informal notion of t%ickness.

%e results of all t%e trials for eac% of t%e com*ounds were as follows' ?.II / =,LI

wit% a *ercent error of ;.H?- / =,L *ercent error for water ??.H= *ercent error for

benCene H.=-H *ercent error for c%loroform >+.,> *ercent error for met%anol -,.HI

*ercent error for t%e unknown liquid.

Wit% t%ese data acquired by t%e re*orters earlier in t%e e/*eriment&

"iscositycoefficient was sol"ed simultaneously using t%e equation' M D / 6 nr N D / t8 A Ɲ

;

>

sim*lified equation w%ere in DM density& nrM "iscosity coefficient& tM time in seconds

(t is belie"ed t%at muc% of t%is error is caused by t%e misalignment of t%e Ostwald

"iscometer. One degree of misalignment introduces = error. Anot%er source of error in t%e

"iscometer is t%e requirement to use t%e e/act "olume of liquid for t%e reference liquid and

t%e test liquid. %is requirement becomes furt%er *roblematic if t%e measurements are done at

different tem*eratures. %e accurate knowledge of density is necessary to ad5st t%e colume at

different test tem*eratures. 2ore error mig%t %a"e been caused by t%e u*rig%tness of t%e

ironstand used in t%e e/*eriment.


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Chapter 4

CONCLUSION AND RECOMMENDATION

%e determination of t%e rate of flow t%roug% a rigid ca*illary is t%e basis for an

im*ortant met%od for t%e measurement of "iscosity. (n t%is met%od& t%e time of outflow of a

known "olume of liquid t%roug% a ca*illary under t%e influence of gra"ity is determined. (n

t%is e/*eriment& t%e re*orters concluded t%at t%e "iscosity of many liquids decreases as t%e

tem*erature increases and "ice "ersa. %e "iscosity of a liquid also de*ends u*on t%e siCe&

slo*e& and c%emical nature of t%e molecules w%ic% com*ose it. %emical forces between

neig%boring molecules also influence "iscosity. And t%e "iscosity of a liquid increases& w%en

it is sub5ected to increased *ressure. As t%e *ressure is increased& t%e molecules are crowded


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more closely and t%ey %a"e less free s*ace left in w%ic% t%ey can mo"e. As t%e tem*erature is

raised& t%e liquid e/*ands and t%e a"ailable free s*aced is increased. (n eac% case& t%e c%ange

of "iscosity *arallels t%e free s*ace in w%ic% t%e molecules can *ass eac% ot%er. All of t%e

"iscometer *arameters can be determined t%roug% careful measurement of t%e "iscometer

dimension %owe"er& t%e "iscometer constant is generally determined by calibration using a

fluid of known density and "iscosity.

(t is well to em*%asiCe t%ose two absolute necessities for satisfactory "iscosity

measurements are cleanliness of t%e "iscometer and an accurate tem*erature control. Ostwald

"iscometer s%ould be cleansed t%oroug%ly before and after e"ery trial of t%e e/*eriment.

ontamination may occur if t%e a**aratus was not cleansed and t%is may greatly affect t%e

"alues of t%e "iscosity of t%e liquid sam*le. %e "iscometer must was% se"eral times by

distilled water and be sure t%at it is totally dried before doing anot%er trial.

-

?

%e "iscometer s%ould "ertically clam* to t%e iron stand. ilted "iscometer may affect

t%e time s*ent of t%e liquid as well as t%e reading at w%ic% it *asses t%e calibration marks.

%e re*orter w%o reads t%e liquid *asses t%e calibration marks s%ould be attenti"e in

recording t%e time to a"oid errors.


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AENDI! A

Tab"es a#$ %&'(res

COMOUND TIME )s* MEAN TIME

)s*

rial + rial 2 rial 3

Water =>.?? s =-.+ s =-.=; s =-.=I s

BenCene +>.I s +>.?= s +>.-I s +>.> s

%loroform . s .=H s .I, s .+? s

2et%anol .>= s .> s .H s .;;> s

Unknown I. s I.> s .-? s I.=;->s

DENSITY )',-L* MEAN

DENSITY


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rial + rial 2 rial

Water = P +I deg.

elsius

,.???? P +.H

deg. elsius

,.?; P + deg.

elsius

,.?-;; P +.H

deg. elsius

BenCene ,.->;H P +I

deg. elsius

,.->II P +I

deg. elsius

,.Q->I? P +

deg. elsius

,.->; P +.H

deg. elsius

%loroform =.I;?H P +

deg. elsius

=.I>, P +H

deg. elsius

=.I;-? P +

deg. elsius

=.I?; P +.;>

deg. elsius

2et%anol ,.>? P +I

deg. elsius

,.>? P +I

deg. elsius

,.>?I> P +I

deg. elsius

,.>?-P +I

deg. elsius

Unknown ,.;H-; P +I

deg. elsius

,.;H?H P +I

deg. elsius

,.;H?- P +I

deg. elsius

,.;H? P +I

deg. elsius

ISCOSITY COE%%ICIENT ) 8 Ɲ MEAN ) 8 Ɲ

rial + rial 2 rial 3

Water ?.+? / =,L I ?.I> / =,LI ?.H?? / =,LI ?.II / =,LI

BenCene =.+IHI / =,L =.+;> / =,L =.+? / =,L =.+-=? / =,L

%loroform +.H>; / =,L I +.?;? / =,LI +.>+? / =,LI +.HHH- / =,LI

2et%anol =.H+; / =,LI =.H=?= / =,LI =.H++- / =,LI =.H++H / =,LI

Unknown =.I;-; / =,LI =.I?=H / =,LI =.I,IH / =,LI =.IHI? / =,LI

able .= Data %eet for Water& BenCene& %loroform& 2et%anol and Unknown :iquid

=,

++

&ct(res /0 Apparat(s (se$:

a8 Ostwald "iscometer b8 West*%al balance c8 %ermometer

Used to measure distance Used to measure t%e Used to measure t%e

t%e liquid tra"els density of a liquid tem*erature


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d8 9eagent bottle e8 rubber tubing f8 *i*ette *um*

w%ere liquids stored Used as a *assage for liquid or Used to *um* air gas in e/*eriments

'* Ir/# sta#$ h* c"a-p 1It s(pp/rts the -&t(re 1Use$ sec(r' the &sc/-eter

AENDI!

COMUTATIONS

=8 Water 6rial =8 '

tM e/* 6= R +N R ln R I L H8 Ɲ=M H+.-I

+M >,.;

M H.-;;IM H.->? / =,L+?

t6true "alue8 M e/* S6H+.-I R 6>,.;N+IR+>.=H8 R H.-;; ln 6+I R +>.=H 8 R H.->? / Ɲ=,L+? / 6+.H R +>.=H8L=, Q

t 6true "alue8 M ?. I>> / =, LI !as Ɲ


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=M e/* SH+.-I R 6>,.;N+I R +>.=H8 R H.-;; ln 6+I R +>.=H 8 R H.->? / =,L+? / 6+I ƝR +>.=H8L=, Q

=M ?.+? / =,LI !as Ɲ

2ean =M 6?.+? / =,L I R ?.I> / =,LI R ?.H?? / =,L I8N M ?.II / =,LI !as Ɲ

+8 BenCene 6rial =8

=M >.H=>+M +,?I.;-

M +.>?I

IM ,

HM ,

t 6true "alue8 M e/* S>.H=> R +,?I.;-N+.HR+>.=H R +.>?I ln 6+.H R +>.=H8 R , 6 +.H R Ɲ+>.=H8L, Q

t 6true "alue8 M ,.+;? !a / s 6rue Value8 Ɲ

M D / 6 nr N Dr / t8 M Ɲ0.8765

g

mL ×27.4 s [

9.3293 x10−4 Pa−s

1 g

ml x17.99 s

] M =.+IHI /=,L !a /

mean +M 6=.+IHI / =,L R =.+;> / =,L R =.+? / =,L 8 N M =.+-=? /=,L !a / Ɲ

=+

=

8 %loroform 6rial =8

=M =I.=,?+M =,I?.+

M ,.H>>

IM ,HM ,

t 6true "alue8 M e/* S=I.=,? R 6=,I?.+N +.;>R +>.=H8 R ,.H>> ln 6+.;> R+>.=H8 R , Q Ɲ

t 6true "alue8 M H.IH?I / =,LI Ɲ


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M D / 6 nr N Dr / t8 M Ɲ1.4695

g

mL ×3.33 s[

9.3293 x 10−4 Pa−s

1g

ml x 17.99 s

] M +.H>; /=,L I !as

mean M 6+.H>; / =,LI R +.?;? /=,LI R +.>+? / =,LI8 NM +.HHH- /=,LI !as Ɲ

I8 2et%anol 6rial =8

= M +H.=>

+M =>-?.+ M +.,;?

IM ,

HM ,

t 6true "alue8 M e/* S+H.=> R 6=>-?.+N +IR +>.=H8 R +.,;? ln 6+IR+>.=H8 R , Q Ɲ

TtM H.IH=; / =, LI !a 6true "alue8

M D / 6 nr N Dr / t8 M Ɲ0.7933

g

mL ×3.71 s[

9.3293 x 10−4 Pa−s

1g

ml x 17.99 s

] M =.H+; /=,L I !as

mean ƝM 6=.H+; / =,LI R =.H=?= /=,LI R =.H++, / =,LI8 N M =.H++H /=,LI !as

H8 Unknown 6rial =8

M D / 6 nr N Dr / t8 M Ɲ0.6586

g

mL×4.3s [

9.3293 x 10−4 Pa−s1 g

ml x 17.99 s

] M =.I;-; /=,L I !as

=M ;.H;=I

+M HI+.+

M .;IIM -.,I-> /=,L>

HM =+.-I

t 6true "alue for unknown8 M e/* S;.H;= R 6HI+.+N6+IR+>.=H88 R.;I ln 6+IR+>.=H8 Ɲ

R -.,I-> /=,L> 6+IR +>.=H8L=+.-I Q=I

t 6true "alue for unknown8 M >.HIH, / =,L !as Ɲ

!E9ET E99O9

=8 $+,


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errorM S6?.I? / =,L I ?.I /=,LI8 N ?.I> / =,LIQ / =,, M ;.;,+ / =,L=,

+8 BenCene

errorM S6,.+;? =.+-=? / =,L8 N ,.+;?Q / =,, M ??.H=I+

8 %loroform

error M S6H.IH?I / =,L I +.HHH- /=,LI8 N H.IH?I / =,LIQ / =,, M H.=-H

I8 2et%anol

error M S6H.IH=; / =,L I =.H++H /=,LI8 N H.IH=; / =,LIQ / =,, M >+.,>+I

H8 Unknown

errorM S6>.HIH, / =,L =.I;-; /=,L I !as8 N >.HIH, / =,L Q / =,, M -,.HHI

AENDI! C

A$$&t&/#a" r/b"e-s

= (n an e/*eriment wit% an Ostwald "iscometer& t%e times of flow of water and et%anol

are -,s and =>Hs at +,. %e density of water is ,.??-gNcm and t%at of et%anol


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,.>?, gNcm. %e "iscosity of water at +, is ,.,=,,- *oise. alculate t%e "iscosity

of et%a%ol.

)i"en'

T=20°C

t water M -,s

t et%anol M =>Hs

ρwater M ,.??-g

cm³

ρet%anol M ,.>?,g

cm³

F 6water8 M ,.,=,,- *oise

9equired'

F 6et%anol8

olution'

F 6water8 M ,.,=,,- *oise 61

g

cm.s

1 poise8 M ,.,=,,-

g

cm.s

η (ethanol) = (ρ ethanol)(t ethanol)(ηr

ρrtr )

η (ethanol) = (0.790g

cm³ )(175s)(

0.01008g

cm.s0.998 g

cm³(80s)

)

η (ethanol) = 0.0175g

cm.s


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15

=;

+ An e/*eriment was *erformed t%at measured t%e flow of four different liquids as

tem*erature was increased. According to t%e gra*%& w%ic% of t%e liquids %ad t%e

greatest "iscosity at a tem*erature of ,

+

,

E2!E9AU9E 68

, =, +, ,

:egend'

A

B

D

Answer'

%e liquid t%at %as t%e greatest "iscosity at tem*erature , is :iquid D.

%e dimensional formula of coefficient of "iscosity is XXXXXX

Answer'

η = (ρ)(t )(ηr

ρr tr )

I $ow does t%e "iscosity of a liquid c%ange wit% tem*erature


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=>

Answer'

Viscosity of a liquid c%ange wit% tem*erature in a way t%at "iscosity decreases

as is tem*erature increases.

H (n an e/*eriment wit% an Ostwald Viscometer& t%e "iscosity of t%e toluene and water

at , is ,.H>? and ,.-,,> *oise. %e times of flow of water and toluene are I=s

and I.Hs. %e density of water is =.,,+ gNcm. alculate t%e density of toluene.

)i"en'

M,

t water M I=s

t toluene M I.Hs

ρwater M =.,,+g

cm³

F 6water8 M ,.-,,> *oise

F 6toluene8 M ,.H>? *oise

9equired'

ρtoluene

olution'

F water M ,.-,,> *oise 61

g

cm.s

1 poise8 M ,.-,,>

g

cm.s

F toluene M ,.H>? *oise 61 gcm.s

1 poise8 M ,.H>?

gcm.s

F toluene M 6 ρtoluene86t toluene86ηr

ρr tr 8


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,.H>?g

cm.s M 6 ρtoluene86I.Hs86

0.8007 g

cm.s

1.002 g

cm3 (41s)

8

ρtoluene M ,.-;==

g

cm3

RE%ERENCES

Books'

Atkins& !eter W. and de !aula&


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=-

phy chem experiment 3

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