ktu chemistry lab manual
TRANSCRIPT
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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#!$6
im
o determine the chloride ion in a given water sample by #rgentometric method :&ohrs
ðod........ml
.2 Estimation of c-lori(e ion in t-e )i/en ,ater sample
Gi/en ,ater sample /s2 )N!3 In(icator* :.r!>
,oncordant volume of #gA;3solution D2>........ml
Aormality of standard #gA;3 solution A# > A+1'' > '.'1A
Dolume of standard #gA;3solution D# > ?D2D1@
> LLLLLml
Dolume of given water sample D > 5' ml
Aormality of given water sample Acan be calculated from the normality formulaA#x D#> Ax D
i.e. A#x D#> Ax 5'
Aormality of given water sample
> LLLLL..A
#mount of chloride ions > Ax E=. t of ,hlorine > A x 35.45 g+F
> LLLLL..g+F
#mount of chloride ions in ppm > LLLL.N 1''' mg+F or ppm
> LLLLLLmg+F or ppm
RESULT
Sl2
No2
4olume of )i/en
,ater sample in ml
Burette rea(in) in ml 4ol2 of )N!3
solution in ml 54.6initial final
1 5'
2 5'
3 5'
4 5'
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he amount of chloride ion in the given water sample isLLLL..mg+F or ppm
Preparation of rea)ents
12 Preparation of )N!359291 N6C
)issolve 1." g of #gA;3solid :&ol. t. 1%.$%< 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