Lab Manual for IT( 16 Th Dec)

8/19/2019 Lab Manual for IT( 16 Th Dec)

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Chandigarh University, Gharuan

Applied Chemistry Lab Manual (for IT students)

ub!e"t "ode# AC$%&'

Inde

erial

*o+*ame of the eperiment

$age

no

1. Determination of temporary and permanent hardness of given hard water sample by volumetric analysis.

2

2. To determine the amount of residual chlorine present in given water sample. 10

3. To determine viscosity of the given liquid by Ostwalds !iscometer. 1"

". #alibration of the p$ meter. Determination of the p$ of the buffer solutionsand an un%nown solution.

1&

'. To study the synthesis of (spirin )acetylsalicylic acid* using different acid

and base catalysts.21

+. ,reparation of polymer )ma%ing of plasti") from potato starch. 2'

-.

Determination of strength of an un%nown solution of strong acid by titratingit against aO$ solution conductometrically.

2&

To determine )a* / ma of a solution of cobalt chloride )b* verify eerambert law and apply it to find the concentration of given un%nown

solution by 4! spectrophotometer

32

5. To separate and identify the amino acids in a miture by thin layer

chromatography and find out 6 f value of amino acids35

10. Determination of heat of neutrali7ation of sodium hydroide solution

against the solution of hydrochloric acid."3

11. ,ro8ect "5

*ame of the ub!e"t Coordinator# Dr. Debarati #ha%raborty ignature#

ate of issue#

Appli"able to#

1 | P a g e


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-.$-/IM-*T *o+ &

Aim# etermination of temporary and permanent hardness of given hard 0ater sample by

volumetri" analysis

Apparatus# urette9 urette stand9 #onical flas%9 :easuring cylinder9 Dropper

/e1uirement# ;tandard $ard water9 $ard water sample9


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stable.

?hen =DT( is added from the burette9 it combines with all metal ions to form the respective

:etal=DT( complees and indicator become free. (s a result of which blue colour appears in

the titration flas% at the end point.

2bservations#

Titration

tandard 3ard 0ater v4s -TA#

!olume of standard hard water ta%en for each titration E10ml

;olution in burette E


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1

2

3

#oncordant 6eading E FF !3 ml

$ro"edure#

Titration

tandardi9ation of -TA solution#

?ash the glass apparatus with distilled water. 6inse and fill the burette with =DT( and note

down initial burette reading. ,ipette out 10ml of standard hard water in the titration flas%. To this9

add appro. 'ml of buffer solution and 3" drops of =riochrome lac%T indicator. ?ine red

color is obtained. ow titrate it against =DT( till wine red color changes to blue color. ote

down the final burette reading. 6epeate the above procedure 23 times for getting concordant

reading.

Titration #

etermination of total hardness#

Gill up =DT( solution in the burette and note down initial burette reading. ,ipette out 10ml hard

water sample in a washed titration flas%. To this add appro. 'ml of buffer solution and 3" drops

of =riochrome lac%T indicator as a result of which wine red colour solution is obtained. ow

titrate it against =DT( till wine red color changes into blue color which is the end point. 6epeat

the titration 23 times for getting concordant reading.

Titration 7#

etermination of permanent hardness#

Ta%e 100 ml of hard water sample in a '00 ml bea%er and boil gently for half an hour .#ool and

filter it. ,ipette out 10ml of this water and titrate it with =DT( solution in the same manner as in

step 1 and 2. Ta%e three concordant readings.Cal"ulations#

5or the standardi9ation of -TA#

1ml of ;.$.? E 1 mg of #a#O3

!ol. of ;.$.? ta%en for titration E 10ml

et concordant volume of =DT( used E !1

4 | P a g e


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!1 ml of =DT( E 10 ml ;.$.?

10ml of ;.$.? E 10 mg of #a#O3

!1 ml of =DT( E 10 mg of #a#O3

1 ml of =DT( E 10< !1 mg of #a#O3

etermination of total hardness of hard 0ater sample#

!ol. of water sample ta%en for titration E 10 ml

!ol. of =DT( solution used E !2 ml

!2 ml of =DT( E 10 ml of water sample

10ml of water sample E !2 ml of =DT(

10 ml of water sample E !2 H 1 ml of =DT(

10 ml of water sample E !2 H 10

1 ml of water sample E !21000ml of water sample E !2

Total $ardness of water ;ample E !2

etermination of $ermanent 3ardness

!ol. of hard water ta%en after boiling and filtering E10 ml

et vol. of =DT( solution used E !3ml

10 ml boiled water E !3 ml =DT(

E !3H10< !1mg of #a#O3

1 ml boiled water E !3,ermanent hardness of water E !3H1000< !1 ppm

Temporary hardness of hard water sample E Total hardness ,ermanent hardness EI ppm

Total of hard water sample E I1 ppm

,ermanent hardness of water sample E I2 ppm

Temporary hardness of ?ater sample E I3 ppm.

tandard result# Total hardness 1'0300ppm

Deviation )if any* Gor moderately hard water9 total hardness will be in the range of -'1'0 ppm

and for very hard water9 total hardness J 300 ppm

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$re"autions

&+ The glass apparatus should be cleaned and rinsed with distilled water.

+ ower meniscus of burette should be read.

7+ =nd point should be observed correctly.

:+ The amount of indicator added should be same each time.

ignifi"an"e#

1. $ardness tells the category


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ions the minimum p$ of the solution. Gor calcium9 the minimum solution p$ for it to

compleate with =DT( is -.3 while for magnesium9 it is10. Therefore9 the minimum solution p$

of the environment where the reaction occurs is at p$ 10. (t this p$9 #a=DT( is stable and any

magnesium present will not interfere with the reaction. An this eperiment9 =T )=riochrome

lac%T* was used as the indicator. :ost compleometric titrations are performed with

indicators which are themselves chelating agents and whose metal complees have a different

color from the reagents. Andicators having this special property are called metallochromic

indicators.

6I6A%62C-

; 2n boiling ho0 temporary hardness ("arbonate hardness) is removed, eplain<

Ans# Temporary hardness of water is due to presence of bicarbonate salts of calcium and

magnesium i.e.9 calcium bicarbonate and magnesium bicarbonate. These salts are soluble in

water. On boiling9 these salts are converted into carbonates and hydroides of #a and :g which

are insoluble in water and can be easily separated by filtration.

#a)$#O3*2

#alcium bicarbonate

);oluble in water*

:g)$#O3*2

:agnesium bicarbonate

);oluble in water*

;# =hat is a relationship among various units

of hardness<

Ans# 1ppm E 1mg<

Ans# (t higher p$9 #a#O3 or :g)O$*2 may get precipitated and the indicator may change its

7 | P a g e

#a#O3 @ $2O @ #O2#alcium #arbonate

)insoluble in water*

:g)O$*2 @ 2#O2:agnesium $ydroide



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color. (t lower p$ value :gAndicator comple becomes unstable and a sharp end point

cannot be obtained.

;'# =hat are the methods for determination of hardness and 0hy -TA method is

preferred one<

Ans# $ardness can be determined by i* O$ehners method ii* ;oap solution method iii*

=DT( method. Out of these three9 =DT( method gives best results because it is less time

consuming and easy to perform.

;?# 3o0 permanent hardness of 0ater "an be removed<

Ans# ,ermanent hardness of water can be removed by i* imesoda process ii* Neolite process

iii* Aon=change resin

ut the colour change from wine red to pure blue is not sharp with calcium indicator

comple. :g2@ ions have to be added if not present in the hard water.

;@# =hy hard 0ater does not form lather 0ith soap<

Ans# ;oaps are sodium and potassium salts of higher fatty acids. On treating soap with hard

water9 #a2@ and :g2@ present hard water form insoluble #a2@ and :g2@ soaps in the form of

scum . ;o later is not formed till all the hardness causing cations are removed from water.

2#1-$3'#OOa @ #a2@ )#1-$3'#OO*2#a @ 2a@

;odium stearate

);oap*

ppts. of calcium stearate


;# =hy disodium salt of -TA is used for determination of hardness of 0ater and not

-TA<

Ans# =DT( cannot be used as such because of its limited solubility whereas its disodium salts

are soluble and also obtained in highly pure form.

;&># =hy "ompleometri" titration using -TA is not "arried out in a"idi" medium<

Ans# #ompleometric titration using =DT( is not carried out in acidic medium because the

complees of =DT( with divalent metal are stable in basic solutions.;& =hi"h "omple out of the t0o (CaB%-8T or MgB%-8T) 2r (CaB%-TA

orMgB%-TA) is more stable and 0hy<

Ans )#a2@ =DT( or :g2@=DT(* is more stable because =DT( is a headentate ligand and

has si coordination sites to entrap the metal ion and hence forms a very stable 11 comple

with metal ions quic%ly.

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;&# =hat is an a"idi" buffer< Give an eample+

Ans# At is a solution of a miture of wea% acid and its salt with a strong base. B#$ 3#OO$ @

#$3#OOaC is an eample of acidic buffer.

;&7# =hat is a basi" buffer< Give an eample+

Ans# At is a solution of a miture of wea% base and its salt with a strong base. B$ "O$ @

$"#lC is an eample of basic buffer.

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-.$-/IM-*T *o+

Aim# To determine the amount of residual "hlorine present in given 0ater

sample

Apparatus# urette9 urette stand9 Titration flas%9 :easuring #ylinder9 ea%ers9 Dropper.

/e1uirement# 10 PA ;olution9 $ypo solution )


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until the solution becomes pale yellow. ow add 2ml of freshly prepared starch solution in the

titration flas%. The colour of the solution changes to deep blue. ow again run hypo solution

from burette until the solution becomes colorless. This is the end point of the titration. ote

down the final reading. 6epeat the eperiment three times and ta%e the concordant reading.

2bservations#

r+*o+ Initial /eading 5inal /eading 6ol+ Used (ml)

1

2

3

#oncordant !olume E !1 ml

Cal"ulation#

&+ etermination of free "hlorine present in 0ater sample+

1 !1 E 2 !2 )$ypo* )?ater ;ample*

1


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$re"autions#

• ;ha%e the solution vigorously so that PA solution is thoroughly mied with water sample.

• 4se only freshly prepared starch solution.

• ote the end point carefully.

• 6ead the burette readings carefully.

ignifi"an"e#

( chlorine dosage higher than brea% point chlorination means that the chlorine demand of all the

chlorine reactive materials has been completely met. The etra amount of chlorine present in

water is %nown as residual chlorine.

/esult and is"ussion#

#hlorine will liberate free iodine from potassium iodide )PA* solutions at p$ & or less. Theliberated iodine is titrated with a standard solution of sodium thiosulfate )a2;2O3* with starch as

the indicator. Titrate at p$ 3 to " because the reaction is not stoichiometric at neutral p$ due to

partial oidation of thiosulfate to sulfate.

Gor maimum accuracy9 iodometric titrations using starch indicator should be performed at

sample temperatures less than 20 M# )+&M G*. ( Qbac% titrationR is recommended for waters

containing potential chemical interferences. An this case9 a %nown amount of thiosulfate is added

in ecess of the chlorine in the sample. The amount of unreacted thiosulfate is titrated with a

standard iodine solution. Then9 the total chlorine is calculated9 based on the thiosulfate

equivalency in the sample. ?hen mied with chlorinecontaining water9 sodium thiosulphate

reacts with the chlorine according to the equation

a2;2O3 @ #l2 @ $2O SJ a2;0" @ ; @ 2$#l

;odium thiosulphate also reacts with hydrochloric acid )produced in the previous reaction* to

form brea%down products such as sulphur9 salt and water

a2;2O3 @ 2$#l SJ 2a#l @ $2O @ ; @ ;O2

The dose required will vary with the p$ of the water9 but is approimately 2 to - parts sodium

thiosulphate per one part chlorine. At is important to note that sodium thiosulphate will also bind

the chlorine in chloramines9 thereby releasing ammonia. At is important to note that sodium

thiosulphate will also bind the chlorine in chloramines9 thereby releasing ammonia.

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6I6A 62C- ;U-TI2*

; =hy freshly prepared star"h solution is used as indi"ator<

(ns ;tarch solution is hydrophobic colloid and is not stable when allowed to stand for a longer

duration. ( gelatinous mass appears if it is %ept for longer time. At is to be freshly prepared.

;# =hat is the effe"t of overdose of "hlorine added to the 0ater for "hlorination<

(ns =cess of chlorine produces an unpleasant taste and odour. :oreover9 its ecess produces

an irritation on mucus membrane. =cess of chlorine also interferes with the en7ymatic activity

of the digestive system.

;7# =hy is boiled 0ater not &>> safe for drinDing<

(ns oiling %ills only the eisting germs in water9 but does not provide any protection against

further possible contamination during storage.

;:# =hat is the signifi"an"e of breaD point "hlorination<

(ns rea% point chlorination is the amount of chlorine which is required to %ill all the germs

and remove all the impurities present in given amount of water. (mount of chlorine higher than

brea% point chlorination remains in the water as free or residual chlorine which may impart

unpleasant odour and taste to water and ma%es it unfit for drin%ing. Therefore from the

%nowledge of brea% point chlorination we can %now the amount of chlorine required to be added

in the water to ma%e it free from harmful bacteria and germs.

;'# =hat is iodometri" titration<

(ns An iodometric titrations9 an oidi7ing agent is allowed to react in neutral medium or in

acidic medium with ecess of PA to liberate free iodine.

PA @oidi7ing agent A2

Gree iodine is titrated against a standard reducing agent usually with sodium thiosulphate.

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-.$-/IM-*T *2+ 7

Aim#%To find out the vis"osity of a given li1uid using 2st0aldEs 6is"ometer

Apparatus# Ostwalds viscometer9 ;top watch9 #lamp stand9 6ubber tubing

/e1uirement Distilled water9 4n%nown liquid

iagram#

5ig# 2st0aldEs vis"ometer

Theory

!iscosity is the property of a liquid by virtue of which it offers resistance to flow when a stress is

applied over it. An the process of flow the molecule comprising the fluid move against one

another and viscosity arises from what can be termed as the frictional effect of relative motion.

?hen the liquid is flowing in a circular tube9 the flow pattern is called streamlines or viscous or

laminar. The Ostwalds !iscometer method is based on ,oiseuilles equation. This relates the rate

of flow of a liquid through a capillary tube with the coefficient of viscosity and is epressed by

the following equation

E Ur "t,


15/52

, E $ydrostatic pressure of the liquid

Thus the determination of the absolute viscosity by ,oiseuilleVs epression involves the

determination of !9r9 t9 l and ,. The method is however tedious. $ence9 a simpler method is used

wherein we compare the viscosities of the two liquids. Af the coefficient of viscosity of one liquid

is %nown9 then that of the other can be calculated. Af t1 and t2 are the flow times required to flow

for equal volumes of two liquids through the same length of a capillary tube then from equation

)1* we have

1 E Ur"t1,1


16/52

6epeat the same procedure to ta%e 3 readings for noting down the flow time of the given

liquid.

2bservations#%

+*o Time of flo0 of 0ater (t&) (se"+) Time of flo0 of given li1uid (t) (se"+)

1

2

3

:ean Time EFFFsec :ean Time EFF.sec

#oefficient of viscosity of water F& 1-.2+ poise

#oefficient of viscosity of given liquid 2 E WWWWW poise

Density of water d1 E 0.55 g


17/52

6I6A%62C-

;+ =hat is the CG unit of "oeffi"ient of vis"osity<

Ans The #X; unit of coefficient of viscosity is poise.

+ efine vis"osity of a li1uid+

Ans !iscosity is a measure of the resistance of a fluid to deform under shear stress. At is

commonly perceived as Ythic%nessY9 or resistance to flow. !iscosity describes a fluidVs

internal resistance to flow and may be thought of as a measure of fluid friction.

7+ *ame the apparatus to measure the vis"osity of a li1uid<

Ans# !iscosity can be measured with the help of an apparatus %nown as viscometer.e.g.

Ostwalds viscometer9 6edwood viscometer

:+ =hat is the effe"t of temperature on vis"osity of li1uid<

Ans The viscosity of a liquid is directly affected by temperature because heat causes molecules

to move farther apart and low temperature causes molecules to come closer together. (t

lower temperatures the viscous material will be thic%er and at high temperatures it will be

thinner.

'+ =hat are the various fa"tors that affe"t the vis"osity<

(ns 1* Ancrease in temperature results in a decrease of viscosity by about 2 per degree.

2* The presence of solutes9 lyophilic colloids and other suspended impurities tend toincrease the viscosity of liquids.

3* ,olarity also affects the viscosity )polar compounds are more viscous than the non

polar*.

"* $ydrogen bonding in a molecule also increases the viscosity.

'* ranched chain compounds possess greater viscosity than straight chain ones.

+* Ancrease in molecular weight increases the viscosity of the liquid.

?+ =hat is vis"osity inde<

(ns !iscosity inde is the variation of a liquid with temperature.

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-.$-/IM-*T *o+ :

Aim# Calibration of the digital p3 meter+ etermination of the p3 of the

buffer solutions and an unDno0n solution

Theory# :ost of the chemical and biochemical processes are affected by the acidity and

al%alinity of the medium in which they ta%e place. ;o9 p$ measurement is valuable information

for a reaction to occur. p$ is a measure of the acidity or al%alinity of a solutionL p$ of a solution

can be represented as follows9

p$E log B$@C

An case of water or any neutral solution9 p$ E -

Gor acidic solution9 p$ K -

Gor al%aline solution9 p$ J -

Apparatus# Digital p$ meter9 bea%er9 tissue paper9 distilled water9 uffer tablet )p$ " and 5*9

bea%er )100 ml*9 hydrochloric acid9 sodium hydroide solution.

$ro"edure#

tandardi9ation of the instrument#

1. ;witch on the instrumentL wait for 101' minutes so that it gets warmed up.

2. ,repare the buffer solution of p$ " and 5 using buffer tablets3. Gunction %ey was set to stand by position.

". Temperature of the buffer -.0 is recorded and the temperature %nob is set to the measured

temperature.'. The electrode is washed several times with distilled water9 dried with clean tissue paper

and then immersed in the buffer solution of p$ -.0.

+. Gunction %ey is set to p$ position and wait for reading to stabili7e.-. #alibrate switch is ad8usted to display the correct p$ of buffer -.0 at measured

temperature. (fter noting the p$ value9 the p$ meter is reset to position.&. The electrode is washed with distilled water9 dried using tissue paper and the n dipped in

a solution of p$ ".0 or 5.0 )Depending on the p$ value of the sample*.

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5. ;tep + was repeated. ow slope control %ey is ad8usted to display the correct value of the

second buffer at measured temperature.10. ;teps '5 was repeated with buffer solution with p$ -.0 )ad8usting calibrate* and buffers

".0 and 5.2 )ad8usting slope control %ey* once or more until the p$ meter displays the

correct values of both buffers without the need of further ad8ustments. The reading should

be correct within one count.

11. (fter p$ meter is standardi7ed9 it is ready for measurement of the p$ of the sample.12. 6inse electrodes with distilled water and dried with tissue paper. ;et the function %ey to

standby position9 measure sample temperature and set temperature value on manual

temperature %nob. Dip the electrode in sample solution 9 set meter to p$ position9 wait for

reading to stabili7e and the reading is recorded.

tandard result p$ value depends on the nature of solution ta%en for analysis. '

deviation is accepted from actual result.

$re"autions#

1. An between measurements9 always set function %ey to stand by position.

2. uffer solution should be prepared only before use. The buffer value is li%ely to change

due to #O2 absorption and contamination.3. (lways cap the buffer containers tightly to prevent ingress of moisture and #O2

absorption.

". 4sed buffer should not be poured bac% into bottles for reuse. This is li%ely to cause errors

in measurement due to possible contamination and degradation.

'. The glass electrode should be stored in distilled water.

+. ;tandardi7ation should invariably be done when changing from acidic range and vice

versa.

6I6A%62C-

1. ?hat is the effect of temperature on p$Z

(ns. (s B$@C increases with increase in temperature9 so p$ value also increases with

temperature.

2. ?hat are buffersZ

(ns. uffers are solutions of %nown p$ which resist the changes in p$ when small

amount of acid or al%ali is added to it.

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3. Xive eample of one acidic buffer and one basic buffer.

(ns. (cidic buffer #$3#OO$#$3#OOa

asic buffer $"O$ #$3#OO$"". ?hat is the effect of temperature on p$Z

p$ value of the solution increases with increase in temperature.

'. ame three electrodes. ?hich are usually employed to measure p$ of a solutionZ$ydrogen electrode9 [uinhydrone electrode and Xlass electrode.

Xlass electrode is most suitable for this purpose. Xlass electrode is simple9 not easily

oidi7ed and attains equilibrium rapidly.

-.$-/IM-*T *o+ '

Aim# To study the synthesis of Aspirin (a"etylsali"yli" a"id) using different

a"id and base "atalysts

Apparatus# Two Test tubes9 Test tube stand9 :easuring cylinder )10 ml*9 two erlenmeyer

flas%s )'0ml*9 two bea%ers )100 ml* and one bea%er )'00 ml*9 Dropper9

20 | 5 0


21/52

/e1uirement# ;alicylic (cid )2.0 grams*9 (cetyl chloride )" ml*9 ,yridine )' drops*9 ;ulphuric

acid )' drops*.

Theory# (spirin is an analgesic antiinflammatory drug. At is one of the oldest and widely used

drugs in medicine. (spirin is synthesi7ed by using acetic anhydride or acetyl chloride to salicylic

acid. (spirin can be synthesi7ed from salicylic acid by using either acid catalyst or base catalyst.

OHO

O

CH3

O

Aspirin

Chemi"al /ea"tion#

+H3C Cl

O

OHO

OH

O OH

O

O

CH3

Salicylic acid Acetyl chloride Acetylsalicyclic acid

Acid

or base catalyst

$ro"edure#

Two thoroughly cleaned test tubes were labeled as ( and . 1.0 gm of ;alicylic (cid was

placed in each test tube. "ml of (cetyl chloride was measured using a 10ml graduated cylinder.

2.0 ml (cetic (nhydride was poured in each test tube.

;ulfuric (cid )' drops* was added to test tube ( with constant stirring. The change was noted

)physical change


22/52

Two '0 ml =rlenmeyer flas% was ta%en and 2' ml of distilled water was poured into the

flas%. The contents of the two test tubes )( and * were poured separately into each '0 ml

=rlenmeyer flas%. ( small amount of distilled water was used to rinse the test tubes to ensure that

all solution was transferred to both flas%s. oth flas%s were cooled in ice water bath for 101'

min to ensure complete crystalli7ation. Af necessary9 a glass stirring rod may be used to scrap the

bottom of the flas% to induce crystalli7ation.

The content was filteredL the contents and filter paper were transferred onto the watch

glass. The watch glass and contents were placed in the drawer and allowed to dry for a wee%.

( wee% later9 the mass of (cetylsalicylic (cid was recorded. The melting point was

recorded. The theoretical melting point of (cetylsalicylic (cid is 13+M#.

/esult#

An both eperiment9 1 g ;alicylic (cid ):.? 13&.12* was reacted with 2m (cetyl

chloride to afford (cetylsalicylic (cid or (spirin ):. ? 1&0.1'-*. The following equations help

determine the limiting reagent.

1g Salicylic Acid×1mol Salicylic Acid

138.12g =0.0072mol Salicylic Acid

2ml Acetic Anhydride × 1mol Acetic Anhydride

102.09 g =0.021mol Acetic Anhydride

An this reaction9 ;alicylic (cid is the limiting reagent because there are fewer moles and

therefore sets the maimum amount of capable of being made.

The theoretical yield is determined using the equations below.

0.0072molSalicylic Acid ×1mol Acetylsalicylic Acid

1mol Salicylic Acid =0.0072mol Acetylsalicylic Acid

0.0072mol Acetylsalicylic Acid × 180.157 g Acetylsalicylic Acid

1mol Acetylsalicylic Acid =1.3 g Acetylsalicylic Acid

Limiting /ea"tant ;alicylic (cid

Theoreti"al Jield 1.3 g

A"tual Jield in "ase of

sulphuri" a"id (g)

$er"ent /e"overy in "ase of

sulphuri" a"id ()

22 | 5 0


23/52

A"tual Jield in "ase of

pyridine (g)

$er"ent /e"overy in "ase of

pyridine ()

The theoretical melting point of (cetylsalicylic (cid is 13+M#. The recovered

(cetylsalicylic acids in each case were recorded.

A"etylsali"yli" A"id Melting $oint

Theoretical Melting Point 13+M#

Recorded Melting Point (in case of sulphuric acid)

Recorded Melting Point (in case of pyridine)

An this eperiment9 two different catalysts were used );ulfuric acid and ,yridine* in test

tubes (]9 respectively. The pPa values of ,yridine and ;ulfuric acid are '.2' and 3

respectively. ,yridine was the basic catalyst in this eperiment and sulfuric (cid was the acid

catalyst in this reaction.

$re"autions#

(ll chemicals were disposed off properly. (queous filtrates were diluted and flushed

down the drain. The (cetylsalicylic (cid was placed in the appropriate organic waste container.

6I6A%62C-

; &+ =hy one "an get smell of a"eti" a"id from a old bottle of Aspirin<

The reason that a bottle of old (spirin might smell li%e acetic acid is because the

acetylsalicylic acid undergoes hydrolysis leaving ;alicylic (cid and (cetic (cid. This occurs

when moisture is introduced to the (spirin. The water molecules in the air react with the (spirin

causing hydrolysis. The hydrolysis reaction is depicted below

23 | 5 0


24/52

OHO

O

CH3

O

Aspirin

+ OH2

OH

OHO

+OH CH3

O

Water Salicylic Acid Acetic Acid

; + =hy Aspirin is used instead of sali"yli" a"id as an analgesi"<

Traditionally9 many pains were treated with salicylic acid. ;alicylic acid is great for

treating painsL however it is highly acidic and damaging of mucous membranes. One way to get

the benefits of salicylic acid without its irritating characteristics is to add an acetyl group to it.

This new compound is %nown as (cetylsalicylic (cid9 commonly %nown as (spirin. This new

compound was first isolated by Geli $offmann. $offmann wanted to find a medicine that was

as effective at treating pain as salicylic acid9 but without the irritating and damaging side effects.

$e too% salicylic acid and found that covering up the acidic part of salicylic acid with an acetyl

group greatly decreases the acidity and damaging side effects. )$offman*H

6eferences

H$offman9 ucas. Y(spirin 101Y 01 (pril 2000. $ow;tuff?or%s.com.

Khttp


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-.$-/IM-*T *o+ ?

Aim# $reparation of polymer (maDing of plasti") from potato star"h,

Theory# An this activity students will ma%e a plasti" from potato starch and investigate the effectof adding a Kplasti"i9erE on the properties of the polymer. ;tarch is made of long chains

of glucose molecules 8oined together. At contains two polymers amylose which is straight

chained and amylopectin which is branched. ?hen starch is dried from an aqueous

solution it forms a film due to hydrogen bonding between the chains. $owever9 the

amylopectin inhibits the formation of the film. 6eacting the starch with hydrochloric acid

brea%s down the amylopectin9 forming more satisfactory film. This is the product that

students ma%e without propane19 29 3triol. The straight chains of the starch )amylose*

can line up together and although this ma%es a good film9 it is brittle because the chains

are too good at lining up. (reas of the film can become crystalline9 which causes the

brittleness.

Section of a starch molecule(amylose and amylopectin)

(dding propane19 29 3triol ma%es a difference due to its hydroscopic )water attracting*

properties. ?ater bound to the propane19 29 3triol gets in amongst the starch chains and stops

the crystalline areas from forming9 preventing the brittleness and resulting in more _plastic

25 | 5 0


26/52

properties9 thus acting as a plastici7er. This can be eplained to students that the propane19 29 3

triol acts as a plastici7er.

Apparatus# 2 bea%ers )2'0 ml*9 watch glass9 hot plate9 stirring rod9 petri dish9 universal

indicator paper9 pipettes9 measuring cylinder )2' ml and 10 ml*.

/e1uirement# Dilute hydrochloric acid )0.1 :9 10 ml*9 dilute sodium hydroide )0.1 :9about 10 ml*9 potato starch )& g* and propane 19 29 3triol )2 ml*

$ro"edure#

1. :a%ing the plastic film

a+ ,ut 22 ml of water into the bea%er and add " g of the potato starch9 3 ml of hydrochloric

acid and 2 ml of propane19 29 3triol.

b+ ,ut the watch glass on the bea%er and heat the miture using the unsen burner. ring it

carefully to the boil and then boil it gently for 1' mins. Do not boil it dry. Af it loo%s li%e it might9

stop heating.

"+ Dip the glass rod into the miture and dot it onto the indicator paper to measure the p$.

(dd enough sodium hydroide solution to neutrali7e the miture9 testing after each addition with

indicator paper. òu will probably need to add about the same amount as you did of acid at the beginning )3 ml*.

d+ ,our the miture onto a labelled petridish and push it around with the glass rod so that

there is an even covering.

e+ 6epeat the process without propane19 29 3triol.

f+ abel the mitures and leave them to dry out. At ta%es about one day on a sunny windowsill9

or two days at room temperature.

/esults#

;tudents should be able to see a difference in the two films that they ma%e. The one without the

propane19 29 3triol is far more brittle9 the one with it shows more plastic properties.

$re"autions#

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1. Do not let the miture boil to dry9 or it _pops and has a tendency to 8ump out of the

bea%er. Gor this reason9 students should wear eye protection at all stages.

2. Af too much water is used9 then their polymer wont solidify and remains a liquid.

6I6A%62C-

1. Define a polymer.

(ns ( high molecular mass giant molecule formed by lin%ing together of a large number ofsmall molecules of monomers.

2. Define thermoplastic and thermo setting plastic(ns ( polymer9 which can be softened on heating and hardened on cooling reversibly.

=ample9 ,!#.

( polymer which during moulding process get hardened and once set9 it cannot besoftened again.

=ample9 ,henol formaldehyde resin

3. ?hat is addition polymeri7ationZ

(ns (ddition polymeri7ation is a reaction that yields a product which is eact multiple of

the original monomeric molecule. =ample polyethene

". ?hat is condensation polymeri7ationZ

(ns #ondensation polymeri7ation is an intermolecular combination though different

functional groups present in the monomer9 with the elimination of small molecules li%e $2O.

=ample ylon++

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-.$-/IM-*T *o+

Aim# etermination of strength of a given hydro"hlori" a"id solution by

titrating it against sodium hydroide solution "ondu"tometri"ally+

Apparatus# #onductometer9 burette9 pipette.

/e1uirement# Distilled water9


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2. Ta%e '0 m


30/52

;. o. !olume of aO$ solution )m* Observed conductance )mho1*

1

2

3

"

'

;uppose volume of aO$ used at equivalence pointE ( m

(pplying normality equation9 1!1E 2 !2 where 1E strength of $#l solution and

2E strength of aO$ solution E


31/52

2. ?hat is specific conductance and what are its unitsZ

(ns ;pecific conductance is defined as the conductance of 1 cc of the solution. Ats unit is

denoted by Pappa ) * and its units are ohmⱩ 1 cm1 or mho cm1.

3. ?hat is equivalent conductance and what are its unitsZ(ns =quivalent conductance )=eq* is the conductance of all the ions produced by dissociation by

1 gm equivalent of a solute in solution and its units are ohm 1 cm2 g9eq1

". ?hat is the effect of dilution on conductanceZ

(ns #onductance increases with dilution because on dilution dissociation increases and hence

the number of ions increases.

'. ?hy ordinary water is unsuitable for conductivity measurementsZ ?hat is conductivity

waterZ

(ns Ordinary water is unsuitable for conductivity measurements because it possesses large

conductance due to the materials dissolved in the container and due to #O2 and $3 dissolvedfrom air. ;o water is specially purified by distilling it a number of times after addition of little

P:nO". ;uch water is called conductivity water and their conductivity should not be more than2 3 10& ohm1.

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-.$-/IM-*T *o+ @

Aim# To determine (a) ma of a solution of "obalt "hloride (b) verify 8eerEs la0

and apply it to find the "on"entration of given unDno0n solution by

spe"trophotometer

Apparatus ;pectrophotometer9 ea%er9 Tissue paper

/e1uirement# Distilled water and cobalt chloride solution of different concentrations

Theory

?hen an electromagnetic radiation is passed through a sample9 certain characteristic

wavelengths are absorbed by the sample. (s a result the intensity of the transmitted light is

decreased. The measurement of the decrease in intensity of radiation is the basis of

spectrophotometry. Thus the spectrophotometer compares the intensity of the transmitted light

with that of incident light.

The absorption of light by a substance is governed by ambert eers law. (ccording to

this law when a beam of monochromatic light of intensity )A0* passes through a medium that

contains an absorbing substance9 the intensity of transmitted radiation )A* depends on the length

of the absorbing medium and the concentration of the solution. :athematically it can be

represented as

(bsorbance E log )A0


33/52

( plot between absorbance and concentration is epected to be a straight line plot9 passing

through the origin9 shows that ambert eers law is obeyed. This plot can be used to find the

concentration )or strength* of a given solution.

$ro"edure#

tep Initial etting of pe"trophotometer#

#onnect the instrument to the power supply. ;et the switch at O position. efore starting the

eperiment ensure that the meter initially reads 7ero on transmittance scale )T*. (d8ust the

wavelength %nob to the required wave length region on scale. ;et the position of gain selector

switch corresponding either to 3"0"00 nm or "005+0 nm wavelengths. (d8ust the set 7ero %nob

so that meter needle reads 7ero on T ;cale and 100 on OD )optical density* ;cale.

tep # 5inal etting of pe"trophotometer.

Open the lid of the sample housing and insert a cuvette containing blan% solution )distilled

water*. #lose the lid so that it fits properly. (d8ust the control %nob )set 100* in appropriate

direction to bring the needle to 100 on transmittance or 7ero on optical density. Open the lid and

remove the cuvette. #lose the lid tightly. #hec% 7ero on the meter and ad8ust to 7ero if disturbed.

6epeat the procedure again for 7ero and 100 Transmittance.

tep 7# etermination of ma

Ansert the cuvette containing standard solution in the similar fashion as eplained in the step

above. ote down the reading of OD at 7ero wavelength. #hange the wavelength with the

increment of 20nm every time and note down the value of corresponding OD. ,lot a graph

between wavelength on ais and OD on yais. The value of / ma can be determined by

etrapolation of the curve towards ais. The maima in the curve gives the value of / ma

tep :# 6erifi"ation of 8eerEs La0 i+e+ etermination of UnDno0n Con"entration

Gi the wavelength of / ma position. ,repare the standard solution as well as having different

concentrations ranging from 20 to 100 of cobalt chloride in distilled water. ote down the

optical density of solutions of different concentrations of cobalt chloride prepared above. ,lot a

graph between OD and concentration. At should be a straight line. Ta%e a solution of the un%nown

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concentration and note down OD. The concentration of the un%nown solution can be determined

from the graph corresponding to the OD of the solution.

2bservation Table#

6ecord the observations in the following Table

;. o. ?avelength )in nm* (bsorbance or Optical Density

1.

2.

The wavelength at which maimum absorption will ta%e place can be depicted by drawing a

graph between ?avelength )on ais* and Optical density )on yais*.

;. o #oncentration (bsorbance or Optical Density

1 20

2 "0

3 +0

" &0

' 100

+ 4n%nown )let it be #1* y

Con"lusion#

?e %now that

(E log )A0


35/52

Gig 1

Grom the above graph9 the concentration of the un%nown solution can be determinedcorresponding to the observed absorbance )y* the `ais9 the un%nown conc. )# 1* on the Iais

can be noted from the graph.

/esult#

The straight line verifies ambert eers law and the un%nown #oncentration as given by the

graph is WWWWWWWWWW.

tandard result# The graph )absorbance vs. concentration* should be a straight line )as shown in

Gig 1* which verifies ambert eers law and this will give the value of un%nown concentration

by %nowing its absorbance value via 4! spectrophotometer. ' Deviation from the eact

concentration value is accepted.

$re"autions#

1* Gor preparing the standard calibration curve9 dilute solution of %nown concentration should

be used.

2* =nsure that you are handling the cuvette with tissue paper .ever touch it with your hand.3* ?ipe the cuvette with tissue paper before placing it in the spectrophotometer.

"* / ma value should be carefully observed.

/esults and is"ussion

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(bsorption spectroscopy can be used to quantify the absorbing species present in the sample.

The greater the quantity of absorbing species present9 the greater will be the etent to which the

incident light will be absorbed. ?hen a beam of monochromatic light falls on a substance9 a part

of it is absorbed and the rest is transmitted. The intensity of the transmitted light is decreased. At

happens that a given material will always absorb light in the same way and not equally at all

wavelengths of light thats why different things are of different colors. ;ome compounds absorb

light outside of the visible light spectrum9 and thats why there are colorless solutions li%e water.

ecause different compounds absorb light at different wavelengths9 a spectrophotometer can be

used to distinguish compounds. (dditionally9 the amount of light absorption is directly

proportional to the distance that the light traveled through a sample and the concentration of

absorbing compounds in that sample.

The primary ob8ective of this eperiment is to determine the concentration of an

un%nown cobalt )AA* chloride solution. An this device9 light will pass through the solution and

stri%e a photocell. The #o#l2 solution used in this eperiment has a light pin% color. ( higher

concentration of the colored solution absorbs more light )and transmits less* than a solution of

lower concentration. The spectrophotometer monitors the light received by the photocell as either

an absorbance or a percent transmittance value. The second part of this eperiment was loo%ing

for the relationship between absorption and concentration of cobalt chloride solution. An fact9 the

absorption would be increased when the concentration rose.

is"ussion of errors and limitation of the eperiment#

There were two main errors happened in the eperiment that may influence or affect this

eperiment9 which were

1. The actual concentration of #obalt )AA* ion solution.

2. The spectrophotometer itself.

Girst9 the actual concentration of #obalt ion solution may be not same as concentration showed

on label. The laboratorymade solution should very accurate and pure. $owever9 during

reserving and moving those solutions into lab9 many factors affect the concentration of solution

36 | 5 0


37/52

by environment. Therefore9 the error of the solution used may transfer into the eperiment and

caused error. Gortunately9 this error should be small and will not affect eperiment seriously.

;econd9 the spectrophotometer may have some instrumental errors in this eperiment. y

calibrating the instrument and using a blan%9 we prevented these errors from becoming too big.

This eperiment required high accuracy of operation and measurement. Therefore9 several

procedures were used in this eperiment to avoid error.

=hat 0as done further to minimi9e error<

Girst9 the accuracy is so importantL the equipment used for measuring should be as accurate as

possible. (lso9 liquids should be measured carefully.

;econd9 the cuvettes had to be rinsed with deioni7ed water9 and the #obalt #hloride solution

before they was filled and placed in the spectrophotometer. An addition9 the outside of tube was

wiped clean to erase any fingerprint oils on the surface of the cuvettes. Ginally9 the test tubes

used to dilute the solutions was dried and not rinsed before being used in order to prevent water

droplets from producing an inaccurate result.

6iva 6o"e#

&+ =hi"h region of ele"tromagneti" spe"trum is taDen into "onsideration during ele"troni"

transitions<

Ans# 4! visible region.

+ tate Lambert 8eerEs la0+

Ans# (ccording to the ambert eers law ?hen a beam of monochromatic light of intensity A0

passes through medium that contains an absorbing substance9 the intensity of transmitted

radiation A depends on the length of the absorbing medium and the concentration of the

solution.

7+ =hat are ele"tromagneti" radiations<

Ans# 6adiations having both electric and magnetic field which oscillate perpendicular to each

other.

:+ =hi"h la0 governs the absorption of light radiations by a sample<

Ans# ambert eers aw.

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'+ =hat does a spe"trophotometer measures<

Ans# ( ;pectrophotometer compares the intensity of transmitted light to the absorbed light.

?+ =hat is the signifi"an"e of linear plot bet0een "on"entration and absorban"e<

Ans# inear plot between #oncentration and (bsorbance verifies ambert eers aw.

+ =hat is the range of U6 6isible radiations<

Ans# 4v radiations 200"00nm and !isible radiations "00&00nm

@+ =hat are the units of =avelength<

Ans# nanometer.

+ & nm "orresponds to ho0 many meter<

Ans# 105

m.&>+ efine transmittan"e and Absorban"e+

Ans# Transmittance The fraction of incident light at a specific wavelength that passes through a

sample.

(bsorbance The fraction of incident radiation that is absorbed by a sample at a specific

wavelength.

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-.$-/IM-*T *2+

Aim# To separate and identify the amino a"ids in a miture by thin layer

"hromatography and find out / f value of amino a"ids

Apparatus# T# ,late9 T# #hamber9 #apillary tubes9 6eagent spray bottle9 ea%ers9 #onicalflas%s.

/e1uirement# 2 solution of individual amino acids9 ;olvent miture of n butanol9 acetic acid

and water in the ratio 123' by volume9 inhydrin reagent

Theory:

Chromatography is the most useful teh!i"ue a#aila$le for the separatio! of

losely relate% ompou!%s i! a mi&ture' (ere the separatio! is a)ete% $y

%i)ere!es i! the e"uili$rium %istri$utio! of the ompo!e!ts $et*ee! t*o

immisi$le phases+ #i,'+ the statio!ary a!% the mo$ile phases' The statio!ary

phase is a porous me%ium li-e silia or alumi!a+ through *hih the sample

mi&ture perolates u!%er the i!.ue!e of a mo#i!g sol#e!t'

Thin layer chromatography is a technique used to separate and identify compounds of interest. (

T# plate is made up of a thin layer of silica adhered to glass or aluminium for support. The

silica gel acts as the stationary phase and the solvent miture acts as the mobile phase.

$ro"edure#

&+ $reparation of thin layer plate#

Dip two clean and dry glass plates held together by crucible tongs into the slurry9 slowly in a

continuous movement. 6emove the slides slowly and allow them to drain on the edge of the

container. ;eparate the slides by handling only the top edges. ,lace them on a sheet of filter with

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40/52

the films facing upwards and dry them for five minutes. 6emove the ecess adsorbent from the

edge.

+ Appli"ations of the sample (spotting the plate)#

(pply two sample drops at least 1 cm apart and about 1 cm above the lower end of the plate. One

of the drops is of the pure amino acid and the other drop is of the miture of the amino acid.

(llow the drops to dry in the air for some time.

7+ evelopment of the "hromatogram#

,repare the developing solvent by miing -0 m of propan1ol with 30 m of concentrated aq.

ammonia. ;oa% a filter paper strip and stic% it to the interior of the 8ar. #arefully introduce the

developing solvent by means of a pipette so that lower edge of absorbent layer is immersed in

the solvent. #over the mouth of the 8ar and allowed chromatogram to develop.

:+ 6isuali9ation of Components

6emove the chromatogram from the developing 8ar. ;pray it with ninhydrin reagent. rown

spots appear on the white bac%ground.

'+ Che"Ding the purity of the sample#

Three spots from the miture of three amino acids9 one above the order will be observed and

their 6 f values can be determined as given below

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6 f E Displacement of the compounds )d1*

Displacement of the solvent front )d2*

?here d1Edistance between centres of the initial spot and the located spot and

d2E distance between centres of initial spot and the solvent front.

$re"autions#

1* ottles containing slurry must be properly stoppered9 since the solvents in which slurry is

prepared are highly volatile.

2* The glass plates must be absolutely clean.

3* The chromatographic plate should be handled with care.

"* There should be a thin or uniform film of slurry on the glass plates.

/esult N dis"ussion#

Different compounds in the sample miture travel at different rates due to the differences in their

attraction to the stationary phase and because of differences in solubility of the solvent. y

changing the solvent or perhaps using a miture9 the separation of components )measured by the

6f value* can be ad8usted.

;eparation of compounds is based on the competition of the solute and the mobile phase for

binding places on the stationary phase. ;ilica gel which is used as a stationary phase is

considered polar ] out of the two compounds which differ in polarity9 the more polar compound

has a strong interaction with silica and is therefore more capable to dispel the mobile phase from

binding places. #onsequently9 the less polar compound moves higher up the plate resulting in a

higher 6f value ] vice versa.

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6I6A%62C-

;+& efine the term "hromatography+

Ans+ #hromatography is an analytical technique used for identification of compounds or

separation of miture of solutes. At is brought about by differential movement of the individual

solutes through a porous medium under the influence of a solvent.

;+ ?hat is adsorption chromatographyZ ame its types.

Ans+ The use of solid as a stationary phase with a liquid mobile phase is %nown as the adsorption

chromatography. At is further subdivided into )i* column chromatography )ii* paper

chromatography and )iii* thin layer chromatography.

;+7 0hat are eluents<

Ans+ The solvents employed for the adsorbed components from the surface of the adsorbent in

column chromatography are called eluents. The solvents used for developing the chromatogram

in T# is also an eluent.

;+: Give the advantages of TLC over paper "hromatography+

Ans+ T# is applied in preferances to paper chromatography on account of the following

advantages.

i* At is far more rapid than paper chromatography and give quic% and reliable results.

ii* ;harp spots are obtained as compared to paper chromatography where the spots are diffused.

iii* (cidic or al%aline solution can be used for the location of spots9which is not possible in paper

chromatography.

42 | 5 0


43/52

iv* The chromatoplates can be heated9if requried.This is not possible in paper chromatography.

v* The spots can be scrapped out for further analysis.

;+' ?hat do you 0ant understand by the term retention fa"tor (/ f )<

Ans+ The movement of any substance relative to the solvent front in a given chromatographic

system is constant and characteristic of a substance. The constant is epressed as 6 f value and is

defined as

6 f E Distance moved by substance

Distance moved by solvent front

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-.$-/IM-*T *2+ &>

Aim# etermination of heat of neutrali9ation of solution of sodium hydroide

against the solution of hydro"hlori" a"id+

Apparatus# #alorimeter9 thermometer9 stirrer.

Theory: The heat of !eutrali,atio! is the "ua!tity of heat e#ol#e% *he! o!e

gram e"ui#ale!t of a! ai% is !eutrali,e% $y o!e gram e"ui#ale!t of a $ase'

/he! stro!g ai%s i! %ilute solutio!s are !eutrali,e% $y stro!g $ases i!

solutio!s of a$out the same o!e!tratio!+ it is fou!% that the heat e#ol#e%

is pratially a o!sta!t "ua!tity for all stro!g ai%s a!% $ases+ #i,'+ 13+700al'

f the ha!ges ourri!g *he! suh solutio!s reat are e&ami!e%+ the

reaso! for this o!sta!t "ua!tity $eomes lear' tro!g ai%s a!% stro!g

$ases i! %ilute solutio! are almost ompletely io!i,e% a!% the same may $e

sai% of the salt forme% $y their u!io!+ so that the o!ly ha!ge may $e sai% to

the formatio! of *ater $y the u!io! of hy%roge! a!% hy%ro&yl io!+ as sho*!

$y the follo*i!g e"uatio!:

a( (Cl aCl (2 13+700 al

( ( (2 13+700 al

Therefore+ heat of !eutrali,atio! of stro!g ai%s $y stro!g $ases represe!ts

the heat of om$i!atio! of o!e gram e"ui#ale!t of hy%roge! io!s *ith o!e

gram e"ui#ale!t of hy%ro&yl io!s to form *ater'

$ro"edure and Cal"ulation#

$art etermination of 0ater e1uivalent of the "alorimeter#

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The heat capacity or water equivalent of a calorimeter is defined as the number of calories

required to heat the calorimeter by 1o# . Af : is the mass of the calorimeter and ; is the specific

heat9 then9 ?ater equivalent E : × ;

1. Girst determine the water equivalent of calorimeter.

2. Ta%e 2' m of distilled water in the calorimeter and record its temperature after every

half minutes.

3. ow ta%e 2' m hot water )higher than room temperature* in a bea%er and note the

temperature after every half minutes.

". (dd this hot water quic%ly to the cold water in the calorimeter and stir the contents well

with a stirrer and note the temperature after every half minutes.

'. ,lot the temperature vs time curve )Gig 1* for all three set of readings.

+. Draw a vertical line at the time of miing )when half of the water has been poured in *

and etrapolate the temperaturetime curve of the hot water and the miture at the time of

miing. The point of intersection will give you the desired temperature.

Gig 1

Time )minutes*

T e m p

t2t3

t1#old water

:i0ing time

. . . .

. . . .. . . .

Cal"ulation#

!olume of cold water ta%en E :1 m

Anitial temperature of water E t1o#

!olume of hot water mied E :2 m

Temperature of water E t2o#

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47/52

Temperature of the mied solution E t3o#

$eat ta%en by the calorimeter and waterE )? @ :1* )t3 t1* #al

?here9 ? is the water equivalent of calorimeter.

The specific gravity of water is ta%en as unity.

$eat given out by hot water E :2 )t2 t3* #al

ow9 heat ta%en up E $eat given out

)? @ :1* )t3 t1* E :2 )t2 t3*

? E :2 )t2 t3* :1 )t3 t1* ÷ )t3 t1*

$art # etermination of the heat of neutrali9ation of sodium hydroide and hydro"hlori"

a"id

1. Ta%e 100 m of 1 $#l in the calorimeter and note the temperature reading after every

half minutes for five minutes.

2. ;imilarly ta%e 100 m of aO$ in the calorimeter and note the temperature reading after

every half minutes for five minutes.

3. Draw temperature time curve for both acid and al%ali solutions.

". ow pour aO$ into the calorimeter containing $#l quic%ly )ta%e care to avoid

splashing*.

'. ;tir and note the eact time of miing.

+. ote the temperature readings after every half minutes for five minutes.

-. (fter the completion of the eperiment9 add a drop of phenolphthalein to ascertain the

completion of the neutrali7ation reaction.

8. ,lot a graph between temperature and time )Gig 2* for all three set of readings.

5. Draw a vertical line at the time of miing )when half of the aO$ has been added in* and

etrapolate the temperaturetime curves at the time of miing. The point of intersection

will give you the final temperature of miing.

47 | 5 0


48/52

Gig 2

T e m p

Time )minutes*

. .

. . . .. .

. . . .

t"

t

t'

:i0ing time

Cal"ulation#

!olume of 1: $#l E :3 m

!olume of 1: aO$ E :" m

Anitial temperature of either $#l or aO$ before miing E t+ o# E )t" @ t' *


49/52

1. ?hen the eperiment is complete9 add a drop of phenolphthalein to the miture of $#l

and aO$. Af a pin% color is seen9 then neutrali7ation is not complete and the eperiment

should be repeated.

2. oth the volume of strength of acid and base should be the same.

3. Ginal temperature should be recorded after thoroughly miing the contents.

6I6A%62C-

&+ =hen atoms "ombine to form a stable bond, the energy is lo0ered+ =here does the

energy go<

(ns At is given out as heat into the QsurroundingsR. This heat is also called enthalpy and the heat

required to brea% 1 mol )+1023* of these bonds is defined to be the bond enthalpy.

+ =hat is enthalpy<

(ns =nthalpy )$* is one of the most important thermodynamic functions in chemistry.

=nthalpy is defined to be the heat echanged at constant pressure. Gor a chemical reaction at

constant pressure )say9 1atm*9 the enthalpy of the reaction9 $rn is defined to be the heat given

out or ta%en in.

?hen9 $rn K 09 the reaction gives out heat to the surroundings so this is an eothermicreaction?hen9 $rn J 09 the reaction ta%es in heat from the surroundings so it is an endothermic

reaction

7+ =hat is "alorimetry<

(ns Xenerally the reactions ta%ing place in the chemical sciences are brea%ing and ma%ing of chemical bonds. This is accompanied by some heat effects. Gormation of chemical bonds

releases energy in the form of heat and hence %nown as an eothermic reaction. The reaction

which is accompanied absorption of heat is %nown as endothermic reaction. #alorimetry is a

scientific term dealing with the changes in energy of the system by measuring the heatechanged with the surroundings. An a broader sense it is defined to determine the heat released

or absorbed in a chemical reaction.

:+ =hat is "alorimeter<

(ns ( calorimeter is a device designed to measure heat of reaction or physical changes and heat

capacity. The device can be sophisticated and epensive or simple and cheap.

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'+ es"ribe the main stru"ture of a "alorimeter+

(ns ( calorimeter consists of two vessels9 outer vessel and an inner vessel. The space between

these vessels acts as a heat insulator and hence there is very little heat echange in between the

inner and outer vessels. Thermometer measures the temperature of the liquid in the inner vessel.The stirrer functions in such a way to stir the liquid to distribute the heat in the entire vessel. The

fibre rings in the calorimeter helps to hold the inner vessel hanging in the center of the outer

vessel. At also has an insulating cover or lid with holes for attaching the stirring rod andthermometer.

?+ *ame t0o different types of "alorimeter+

(. 8omb CalorimeterThe heat of combustion of a compound is measured by placing a %nown mass of a

compound in a steel container called a constantvolume bomb calorimeter9 which is filled

with oygen at about 30 atm pressure. This closed bomb is immersed in a %nown amount of

water. ;ample is added in the sample cup and it is electrically ignited. The heat produced bythe combustion reaction is calculated by recording the rise in temperature of the water.

+ Coffee "up "alorimeter

( constant pressure calorimeter measures the heat effects of variety of reactions such as

neutralisation reactions9 heat of solution and heat of dilutions. ( coffee cup calorimeter is

basically constructed from a polystyrene );tyrofoam* cup with a lid9 in which9 the cup is filledwith a %nown amount of water and a thermometer inserted measures the heat changes associated

with the reaction.

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-.$-/IM-*T *2+ &&

$ro!e"t#

Aim# (long with the prescribed practical syllabus9 every student is required to pursue one

pro8ect during the semester.

ui%eli!es for the proet:

(llocation of pro8ect and collection of samples will be done by the students in unit 1.

The eperimentation part of pro8ect will be eecuted in unit 2.

The analysis ] conclusions of the pro8ect will be drawn and the final report will be

submitted in unit 3.

=ach students should prepare power point presentations on his


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Documents

Lab Manual for IT( 16 Th Dec)