Ktu Chemistry Lab MANUAL

7/26/2019 Ktu Chemistry Lab MANUAL

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General Instructions

1. Students should maintain discipline in the lab

2. Students should obey the instructions given by the faculty members

3. Students should clear the doubts before performing the experiments4. Students are instructed to be punctual in the lab and late comers are not entertained.

5. Experiments will not be repeated if the student is not regular and punctual in the lab

. Students are expected to come prepared and write the procedure in the observation boo!

before performing the experiment.

". #ll the students should submit fair lab record once the experiment is completed

$. #ll the students should wear identity card

%. &obile phones are not allowed in the lab

1'. (ine will be collected from students for the brea!age of glass wares

11. Students are instructed to throw waste in the bin and !eep their wor!bench and

surrounding clean once the experiment is completed

12. )o not waste water and !eep the taps closed while not in use

13. *eep the chemicals in the rac! immediately after use

14. Students should get their observation boo! signed by the faculty before leaving the lab

15. (aculty members can ta!e disciplinary action against students for misbehaving in the lab

1. )o not waste the reagents+chemicals


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Safety Measures

1. ,lean the glass wares thoroughly after use

2. -andle chemicals and apparatus carefully

3. -andle glass wares with utmost care4. Should not add water to acid always add acid to water

5. *eep the windows and doors open

. Should not pipette out acids and toxic reagents by mouth use bulb instead

". *eep the solvents away from burner

$. (ollow the experimental procedure exactly

1'. /se fire extinguishers in case of fire ha0ard

11. Should not wor! in the lab in the absence of lab instructor

12. Should not taste or smell chemicals

13. Switch on the exhaust fans while wor!ing in the lab

14. Should inform the instructor in case of any mishap and should give first aid immediately

15. Should wear lab coat to protect the clothing from chemicals

1. )o not allow the chemicals to come in direct contact with s!in


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List of Experiments

1. Estimation of otal -ardness E)# method

2. Estimation of dissolved oxygen by in!lers method

3. Estimation of chloride in water

4. reparation of /rea 6(ormaldehyde

5. Estimation of 7ron in 7ron ore

. Estimation of ,opper in 8rass

". ,alibration of - meter and determination of - of a solution

$. ,onductivity measurements of salt solutions

%. )etermination of wavelength of absorption maximum and colorimetric estimation of

(e39 in solution1'. )etermination of molar absorptivity of a compound other than (e39

EXPERIMENT NUMBER 1


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ESTIMTI!N !" T!TL #R$NESS !" %TER B& E$T

MET#!$

im

o estimate the amount of total hardness present in the given sample of water by

complexometric titration method using E)#.

Principle

-ardness of water is the property by which water does not give ready lather with soap.

-ardness is mainly due to the presence of bicarbonates chlorides and sulphates of calcium and

magnesium :,a:-,;3


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pparatus re'uire(C 8urette ipette ,onical flas! 8ea!ers (unnel

Rea)ents*'.'1 & E)# solution Standard hard water given water sample Eriochrome 8lac!6

indicator 8uffer solution :A-4,l A-4;-


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of the burette is noted and the titration is repeated to get concordant value. Dolume of E)# used

is ta!en as D2ml.

!0ser/ations an( alculations

12 Stan(ar(i+ation of E$T solution

Stan(ar( -ar( ,ater /s2 E$T In(icator* EBT

,oncordant volume of E)# solution D1>........ml

.2 Estimation of Total -ar(ness of t-e )i/en ,ater sample

Gi/en -ar( ,ater sample /s2 E$T In(icator* EBT

,oncordant volume of E)# solution D2>........ml

12 Stan(ar(isation of E$T

1 ml of standard hard water > 1 mg of ,a,;3

D1ml of E)# solution >2' ml of standard hard water

>2' mg ,a,;3

1 ml of E)# solution >

20

V1

mgC a,;3

.2 Estimation of Total -ar(ness of t-e )i/en ,ater sample

Sl2N

o

4olume of

stan(ar( -ar(

,ater in ml

Burette rea(in) in ml 4ol2 of E$T

solution in ml 5416initial final

1

2

3

4

Sl2N

o

4olume of )i/en

-ar( ,ater sample

in ml

Burette rea(in) in ml 4ol2 of E$T

solution in ml 54.6initial final

1

23

4


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2' ml of the given sample > D2ml of E)#

> D2

20

V1

mgC a,;3

1 ml of given water sample 7 D220

V1

mgC a,;3 120

1''' ml or 1 F of the water sample >V

2

V1 1''' mg ,a,;3

>....................ppm

RESULT

otal hardness of the given water sample >...................... ppm

Preparation of rea)ents

1. Stan(ar( -ar( ,ater sample C1 g of anhydrous ,a,;3is ta!en in a conical flas!. #dd slowly a small amount of

dilute -,l through a funnel to 1 gm of ,a,; 3. 8oil gently to remove ,;2 heat to

dryness in a water bath. )issolve in distilled water and ma!e up the solution to 1 litre.

.2 E$T Solution 5M81996*

)issolve 3."23 gm of disodium salt of E)# of disodium salt of E)# in

distilled water and ma!e up the solution to 1 F with distilled water :weigh exactly 3."23 g

of E)# and then dry in an oven at "5 ', for %' minutes. #fter cooling it has to be

dissolved in distilled water


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ESTIMTI!N !" $ISS!L4E$ !X&GEN 5$!6 IN %TER

SMPLE 5%IN:LER;S MET#!$6

im

o determine the amount of dissolved oxygen :);< in a given water sample by in!lers

method :7odometric method


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#ddition of concentrated -2S;4enables the basic &n;:;-


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pparatus re'uire(C ,onical fla! 8urette &easuring Bar 8ea!ers ipette Ilass rod 7odine

flas! est tube )ropper

Rea)ents*Sodium thiosulphate :Aa2S2;3.5-2; '.'1A


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as D2aml. :7f the water sample has low dissolved oxygen it is recommended to withdraw 2'' ml

for titration


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.2 Estimation of $issol/e( !xy)en 5$2!6

Gi/en ,ater sample /s2 Na.S.!32


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eigh out accurately about '.13g g of *2,r2;"crystals :&ol.wt. 2%4.22 e=.wt. 4%.'35


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ESTIMTI!N !" #L!RI$E I!N IN GI4EN %TER

SMPLE B& RGENT!METRI MET#!$ 5M!#R;S

MET#!$6

im

o determine the chloride ion in a given water sample by #rgentometric method :&ohrs

&ethod........ml

.2 Estimation of c-lori(e ion in t-e )i/en ,ater sample

Gi/en ,ater sample /s2 )N!3 In(icator* :.r!>

,oncordant volume of #gA;3solution D2>........ml

Aormality of standard #gA;3 solution A# > A+1'' > '.'1A

Dolume of standard #gA;3solution D# > ?D2D1@

> LLLLLml

Dolume of given water sample D > 5' ml

Aormality of given water sample Acan be calculated from the normality formulaA#x D#> Ax D

i.e. A#x D#> Ax 5'

Aormality of given water sample

> LLLLL..A

#mount of chloride ions > Ax E=. t of ,hlorine > A x 35.45 g+F

> LLLLL..g+F

#mount of chloride ions in ppm > LLLL.N 1''' mg+F or ppm

> LLLLLLmg+F or ppm

RESULT

Sl2

No2

4olume of )i/en

,ater sample in ml

Burette rea(in) in ml 4ol2 of )N!3

solution in ml 54.6initial final

1 5'

2 5'

3 5'

4 5'


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he amount of chloride ion in the given water sample isLLLL..mg+F or ppm

Preparation of rea)ents

12 Preparation of )N!359291 N6C

)issolve 1." g of #gA;3solid :&ol. t. 1%.$%< in distilled water and dilute to one litre

with distilled water then store in a brown or amber colour bottle.

.2 Preparation of < ? :.r!>in(icator*

)issolve 5 g of #G potassium chromate in 1'' ml distilled water


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EXPERIMENT NUMBER >

PREPRTI!N !" UREC"!RML$E#&$E RESIN

im

o repare /rea(ormaldehyde resin :/( Gesin


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Several molecules of methylol urea derivatives condense with loss of water molecules to

form a linear or highly cross lin!ed urea formaldehyde resin.

/( resins are clear and white and possess better hardness and tensile strength than (

resins. Show resistance to most of the solvents and grease. Excellent abrasion resistance and

stable to light. Iood adhesive characteristics. Iood electrical insulators and possess chemical

resistance. hey can be synthesi0ed in any desired colour by adding proper pigment and filler

during synthesis.

hese resins are widely used in manufacture of buttons bottle caps house hold

appliances surgical items etc. hey are used as adhesives in plywood industries. hey are alsoused in the manufacturing of enamels and other surface coatings. /sed for the finishing of cotton

textiles :hey impart stiffness crease resistance fire retardation water repellence. hey are also

helpful for shrin!age control


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pparatus re'uire(C Ilass rod 8ea!ers (unnel (ilter paper

Rea)ents*/rea :2g


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EXPERIMENT NUMBER =

$ETERMINTI!N !" %4ELENGT# !" BS!RPTI!N

MXIMUM N$ !L!RIMETRI ESTIMTI!N !" "e3D IN

S!LUTI!N

im

o determine the wavelength of absorption maximum and to estimate the concentration

of (e39ion in the given solution colorimetrically.

Principle

,olorimetry is concerned with the visible region of the spectrum and it is the science of

=uantitative estimation of colour and is fre=uently used in biochemical investigations. he

=uantity of light that is absorbed by a solution depends on the concentration of the dissolved

solute that is absorbing the light. 8y measuring the amount of light absorbed we can find the

concentration of solutions. he =uantity of a substance in a mixture can be determined

colorimetrically by allowing the substance to bind with colour forming chromogens. he

difference in colour is directly related to the difference in the absorption of light. o ma!e the

presence of iron visible in solution thiocyanate :S,A< ions are added. hese react with (e39ions

to form bloodred coloured complex.

8y comparing the intensity of the colour of this solution with the colour of a series of

standard solutions with !nown (e39concentrations the concentration of (e39 in the un!nown

solution may be determined.

he colorimetric estimation is based on the BeerCLam0ert;s La,2 he 8eerFamberts law

also !nown as 8eers law or Fambert8eer law is an empirical relationship that relates theabsorption of light to the properties of the materials through which light is passing. 7t states that

the optical absorbance of a chromophore in a transparent solvent varies linearly with both the

sample cell path length and the concentration of the chromophore.


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Beer;s La,

#ccording to 8eers law when monochromatic light passes through the coloured solution

the amount of light transmitted decreases exponentially with increase in concentration of the

coloured substance.

IT7 IoeCkc

Lam0ert;s La,

#ccording to Famberts law the amount of light transmitted decreases exponentially with

increase in thic!ness of the coloured solution.

IT7 IoeCkt

herefore BeerCLam0ert;s la, states that when a monochromatic beam of light is

passed through an absorbing medium the intensity of transmitted light decreases exponentially

with increase in concentrationand t-icAnessof the solution and is given by the expression

IT8Io7 eCkct

here

7> intensity of transmitted light

7o> intensity of incident light

e > base of natural logarithm

! > a constant

c > concentration

t > thic!ness of the solution

he amount of light that passes through a solution is !nown as transmittance.

ransmittance can be expressed as the ratio of the intensity of transmitted light 7 and the

intensity of the incident light 7'. he colorimeter produces an output voltage which varies

linearly with transmittance. he reciprocal of transmittance :absorbance< of the sample varies

logarithmically :base ten< with the product of three factors vi0. molar absorptivity path length t

:width of the cuvette


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density of 1 & solution of thic!ness 1 cm concentration in

moles+F. 7n effect the above e=uation implies that the light absorbed by a solution depends on

the absorbing ability of the solute the distance travelled by the light through the solution :path

length


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should be 5 nm. lot the absorbance vs.wavelength and connect the points to form a smooth

curve.

$escription of t-e spectrop-otometer

Spectrophotometer consists of the following partsC

1. Sources :/D and visible w g

&ass of (e

39

in 4$2.25 (erric alum > 55.$5 g92@3> ) of ferric alum contains 921 ) of iron

&ass of iron in the ferric alum ta!en >0.1x w

0.8634 g

, ) of alum is ma(e up to 199 ml

1 ml of this solution contains >0.1x w

0.8634x100 g of iron

19 ml of t-is solution is ma(e up to 199 ml to prepare t-e stan(ar( solution

1 ml of the standard solution contains >0.1x w

0.8634x100x10 )of iron


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12 $etermination of ,a/elen)t- of maximum a0sor0ance 5max6

%a/elen)t-

5nm6

0sor0ance %a/elen)t-

5nm6

0sor0ance

35' 52'

3"' 54'

3%' 5'

42' 5$'

44' ''

4' 2'

4$' 4'

5'' 5'

avelength of absorption maximum :max< >LLLLLLL..nm

.2 Estimation of "e3Dion usin) colorimeter

4olume of

"erric alum in

ml

0sor0ance

2

4

$

1'

UnAno,n

5

"

Dolume of the un!nown solution used > v1ml

Dolume corresponding to standard solution from the calibration curve > v2ml

/1ml of unAno,n solution is e'ui/alent to /.ml of stan(ar( solution


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&ass of iron corresponding to v2ml of the standard solution >V2x0.1x w

0.8634 g > x )

T-ere for mass of iron correspon(in) to /1ml of t-e unAno,n solution 7 x )

&ass of iron in 1'' ml of the given solution >X x 100

V1

&ass of iron in 1''' ml of the given solution >X x 100x 10

V1 )

RESULT

he concentration of (e39ion the given solution is LLLLL..g+F

Preparation of Rea)ents

12 Preparation of 19? ammonium t-iocyanate solution

)issolve 1' g of ammonium thiocyanate in 1'' ml of distilled water

.2 Preparation of t-e unAno,n solution of ferric alum 5only for instructors6

eigh accurately '.%5 g of the ferric alum in to 1'' ml standard flas!. #dd 1' ml of

,onc. -,l. &a!e up the solution to 1'' ml with distilled water.

1 ml of this solution contains '.'''11 g of iron

(rom this solution give +ml :11 12 13 14 15< as un!nown to students.

E.g. Iive 11 ml to one student. Student should ma!e this to 1'' ml with distilled water. 1

ml of un!nown solution contains '.'''121 g of iron or '.121 mg of iron. 5 and " ml of this ferric

alum solution :un!nown< are accurately transferred in to two 1'' ml standard flas!s. 5 ml of 5A

-,l and 2'J ammonium thiocyanate solution are added and ma!e up the solution to 1'' ml

with distilled water. he optical density or absorbance of the solutions is measured using the

colorimeter by setting the wave length at 4$' nm using a blan! solution. (rom the calibration

curve volume of the standard solution corresponding to 5 and " ml un!nown can be obtained./sing this the mass of iron in the given un!nown solution can be calculated.

EXPERIMENT NUMBER


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$ETERMINTI!N !" M!LR BS!RPTI4IT& !"

!MP!UN$ !T#ER T#N "e3D 5r @D 6

This experiment can be done by two methods (select one method)

"irst met-o(

# more accurate method is to measure the absorbance of several !nown concentrations of

*2,r2;" using a colorimeter. # graph is plotted with absorbance on the axis and

concentrations on the Oaxis. he line will be linear. he slope of the line will give the molar

absorptivity :actually t


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herefore BeerCLam0ert;s la, states that when a monochromatic beam of light is

passed through an absorbing medium the intensity of transmitted light decreases exponentially

with increase in concentrationand t-icAnessof the solution and is given by the expression

IT8Io7 eCkct

he BeerCLam0ert;s la,can also be represented as

lo)IT8Io 7 Cct

here ITand I9are the intensities of the transmitted and incident light and is calledthe

molar absorptivity or extinction coefficient of the chromophore at wavelength :the optical

density of 1 & solution of thic!ness 1 cm molar absorptivity t > cell path length in cm and c > concentration in

moles+F. (or a given substance at a particular wave length the optical density or absorbance is

directly proportional to the concentration of the solution. (or a solution of !nown concentration

absorbance can be measured using colorimeter. -ence we can calculate molar absorptivity : < of

the solution with !nown concentration using 8eer Famberts law.

$escription of t-e olorimeter

Iiven in the previous experiment

pparatus re'uire(C ,olorimeter standard flas! glass rod wash bottle cuvettes

Rea)entsC otassium dichromate :*2,r2;"< solution )iphenyl carba0ide ,onc. -2S;4

Proce(urePreparation of :.r.!=solution ,it- Ano,n concentration

repare a standard solution of chromium by weighing out approximately '."35 g of

potassium dichromate and dissolve it in 25' ml :concentration is '.'1 &


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of standard ,r9solution into different 1'' ml standard flas!s. #dd 1' ml of A - 2S;4and 1 ml

diphenyl carba0ide :allow 1' minutes for colour development< and ma!e up the solution with

distilled water :concentration becomes 1 x 1' to x 1'& '."35 g :m t> 1 cm

&olecular weight of *2,r2;" > 2%4.1$5 g

,oncentration :c< in mole+F >m

294.185 mole+F

&olar absorptivity of potassium dichromate 7A

ct or slope of the graph

&olar absorptivity from the slope of the graph > LLLLmole1Fcm1

RESULT

&olar absorptivity of potassium dichromate > LLLLLL mole1Fcm1or &1cm1

Second !ethod


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im

o determine the molar absorptivity or extinction coefficient :< of potassium dichromate

:*2,r2;"< using Spectrophotometer

Principle

Spectrophotometer and ,olorimeter wor!s on the same principle. 7t is based on 8eer

Famberts law and the principle is given in the previous experiment.

7 ct

here #> absorbance > molar absorptivity t> cell path length in cm :it is 1 cm concentration in moles+F.

pparatus re'uire(C Spectrophotometer standard flas! glass rod wash bottle cuvettes

Rea)entsC otassium dichromate :*2,r2;"< solution of !nown concentration A -2S;4

)iphenyl carba0ide solution

Proce(ure

Measurement of maximum a0sor0ance usin) spectrop-otometer

repare a solution of potassium dichromate with a !nown concentration of chromium.

a!e 1' ml of this solution add 1' ml of A - 2S;4and 1 ml diphenyl carba0ide :allow 1'

minutes for colour development< and ma!e up to 1'' ml with distilled water. 8lan! solution is

used as the reference.he absorbance of the solution is measured using the spectrophotometer.

&easure the absorbance at different wavelengths in the in the range 35'5' nm usually in

intervals of 2' nm. 7n the region of maximum absorbance the interval should be 5 nm. (ind out

the maximum absorbance.

Steps for operating spectrophotometer

Iiven in the previous experiment

!0ser/ations an( alculations

$etermination of maximum a0sor0ance


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%a/elen)t-

5nm6

0sor0ance %a/elen)t-

5nm6

0sor0ance

35' 52'

3"' 54'3%' 5'

42' 5$'

44' ''

4' 2'

4$' 4'

5'' 5'

&aximum absorbance>LLLLLLL..

&ass of given potassium dichromate > m

hic!ness of the cuvette > t> 1 cm

#ccording 8eerFamberts law A7 ct

Ais the maximum absorbance of the given solution

&olecular weight of *2,r2;" > 2%4.1$5 g

,oncentration :c< in mole+F >m

294.185 mole+F

&olar absorptivity of potassium dichromate 7

A

ct 7

A

c :Since t> 114 is very

al!aline and p-

>" is neutral.

he commonly used electrodes to measure H of a solution are -ydrogen electrode

Puinhydrone electrode and Ilass electrode. he Helectrode commonly used in Hmeasurement

is a combined glass electrode. 7t consists of sensing half cell and reference half cell together

form an electrode system. he sensing half cell is a thin Hsensitive semi permeable membrane

separating two solutions vi0. the outer solution :the sample to be analysed< and the internal

solution :enclosed inside the glass membrane and has a !nown Hvalue


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Electrode Response> E'62.303RT

nF x H

here E'> Standard electrode potential G > gas constant ( > (araday constant >

temperature in *elvin and n > number of electrons involved in the reaction.pparatus re'uire(C Hmeter combined electrode 8ea!er Ilass rod &easuring Qar

Rea)ents* Buffer solutions of H4 H" and H%.2 un!nown solution

Proce(ure

1. ali0ration of P#meter

#ll Helectrode re=uire calibration from time to time. Ensure that Hmeter is on and to

obtain high precision of measurements let the Hmeter to warm up for 3' minutes. Ginse the H

electrode with distilled water and dry the outside of the electrode with a paper towel. Select the

calibration mode on the Hmeter. lace the electrode in to 2' ml of H" buffer solution ma!ing

sure that the Bunction :located on the bottom side of the electrode< is wet :only 1 to 2 inches


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12 Buffer solution of P#>

ransfer a buffer tablet of H4 carefully using forceps to a 1'' ml standard flas!. #dd little

of distilled water crush the tablet and dissolve it. &a!e up the solution to 1'' ml with distilled

water

2. Buffer solution of P#= an( P#2.

,an be prepared in the same way using appropriate buffer tablets

Precautions

1. #lways use fresh Hbuffer solutions for most accurate results

2. Electrodes must be immersed properly in the solution and sufficient time to be allowed

for the electrodes to assume the temperature of the solution

3. (or H

measurements it is desirable to stir the solution4. ;il and grease if present in the electrode layer should be gently removed by wiping

followed by washing with distilled water

5. Electrodes used in Hmeter are highly fragile and hence handle it carefully

EXPERIMENT NUMBER @


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!N$UTI4IT& MESUREMENTS !" SLT S!LUTI!NS

im

o measure the conductivity of salt solutions with a series of !nown concentration and to

calculate the concentration of the given un!nown solution by using conductivity meter.

Principle

Electrolytic conductivity of a solution is defined as the ability or power to conduct

electricity. Solutions of electrolyte conduct electricity by the migration of ions under the

influence of an electric field. Fi!e a metallic conductor they obey ;hms law. Exceptions to this

law occur only under abnormal conditions :very high voltage or high fre=uency currentv

R

Gesistance of a sample of length land area of cross sectionAis given by

$

l

A or G >l

A

,onductance is the reciprocal of resistance Rand its unit is mhos :reciprocal of ohms 1 cm andA> 1 cm2 %> he specific conductance or conductivity of an

electrolyte is defined as the conductance of a solution contained between two parallel electrodes

of unit cross sectional area which are !ept at unit distance apart :unit volumeSpecific conductance(K)

Observed conductance(C)

&'ivalent condctance* 7t is defined as the conducting power of all the ions produced by

dissolving one gram e=uivalent of an electrolyte in a solution. he e=uivalent conductance of an

electrolyte is given by

e'>

1000K

N S7 unit is S cm2e=1

!olar condctance* 7t is defined as the conducting power of all the ions produced by

dissolving one gram mole of an electrolyte in a solution. he molar conductance of an electrolyte

is given by

m>

1000K

S7 unit is S cm2molR1

#t first conductivity meter has to be calibrated. (or this purpose a standard *,l solution

whose conductivity is !nown is used. ,onductivity can be adBusted to the !nown value by using


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the calibration !nob. hen the given electrolyte is ta!en in the conductivity cell and its

conductance is measured. # voltage is applied between the two electrodes in the probe which is

immersed in the sample solution. E=uivalent conductance is calculated using the e=uation given

above.

pparatus re'uire(C ,onductivity meter magnetic stirrer standard flas!s measuring Bar 25'

ml bea!er (unnel

Rea)entsC *,l solution given electrolyte :Aa,l or *,l

Ktu Chemistry Lab MANUAL

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Transcript of Ktu Chemistry Lab MANUAL