Eng.chemsitry Labmanual

Engineering Chemistry Lab Manual (I B.Tech Common to All)

__________________________________________________________________________________Engineering Chemistry SV GROUP OF INSTITUTIONS1

Experiment-1ESTIMATION OF HARDNESS OF WATER BY EDTA

(COMPLEXOMETRY)

Aim: To estimate the hardness of the given Sample water using a standard solution of EDTA.

Apparatus: 100 ml standard flask,Burette,250 ml Conical Flask,20 ml Pipette,& Simple balance with weights,

Chemicals Required: Ethylene di-amine tetra acetic acid (EDTA),Solo-chrome (EBT) Indicator,Ammonia Buffer solution,Hard-water & distilled water.

Principle:Hard water which contains calcium and magnesium ions forms a wine red colored complex

with the indicator, Eriochrome Black-T.

Ethylene diamine tetra acetic acid (EDTA) forms a colourless stable complex with free metalion like Ca, Mg. i.e., Metal + Indicator Metal indicator complex (wine red colour)When EDTA is added from the burette, it extracts the metal ions from the metal ion-indicator complexthereby releasing the free indicator. (The stability of metal ion-indicator complex is less than that ofthe metal ion- EDTA complex, and hence EDTA extracts metal ion form the ion-indicator complex.)

EDTA + Metal indicator complex Metal ion-EDTA + Indicator(Wine red color) (Blue)

The reactions take place at a pH = 10 and the buffer is made by ammonium chloride and ammoniumsolution.

Procedure:

Preparation of standard hard water:Dissolve 0.1g or 100 mg of CaCO3 in minimum quantity of dil.HCl in 100 ml standard flask.

Makeup the solution up to mark with distilled water.1 mL hard water solution = 1mg of CaCO3 equivalent hardness.

Standardization of EDTA solution:Rinse and fill the burette with EDTA solution. Pipette out 20 mL of standard hard water in a

conical flask. Add 2-5 mL of buffer solution and 2 to 3 drops of EBT-indicator. Titrate with EDTAsolution till wine-red colour changes to clear blue. Let volume EDTA solution used be V1 mL.

Titration of Unknown Hard water:Rinse and fill the burette with EDTA solution. Pipette out 20 mL of Sample hard water in a

conical flask. Add 2-5 mL of buffer solution and 2 to 3 drops EBT-indicator. Titrate with EDTAsolution till wine-red colour changes to clear blue. Let volume of EDTA solution used be V2 mL.



Titration of Permanent hardness:Take 200 mL of the water sample in a large beaker. Boil it. Till the volume is reduced to about

50 to 100 mL, filter it, collecting filtrate in a 100 mL standard flask, makeup the volume to 100 mLwith distilled water.

Rinse and fill the burette with EDTA solution. Pipette out 20 mL of Boiled hard water in aconical flask. Add 2-5 mL of buffer solution and 2 to 3 drops EBT-indicator. Titrate with EDTAsolution till wine-red colour changes to clear blue. Let volume EDTA solution used by V3 mL.

Preparation of Standard hard water solution:

W1 = Weight of bottle + substance = ____________ gms

W2 = Weight of bottle = ____________ gms

Weight of substance = (W1-W2) = ____________ gms.

Titration of Standard hard water

Burette ReadingS.No Volume of Standard Hardwater (Vs) Initial Final

Volume of EDTA solutionconsume (V1)

1 20 ml

2 20 ml

3 20 ml

Vs = 20 ml V1 =

V1=

(20 ml Standard hard-water reacting with 20 ml 0.01M EDTA solution)

Titration of Sample Hard water:Burette ReadingS.No Volume of Sample Hard

water (VH) Initial FinalVolume of EDTA solutionconsume (V2)

1 20 ml

2 20 ml

3 20 ml

VH = 20 ml V2 =



V1=

V2 =

Total hardness of water = 1000XV2

V1

Titration of Permanent hardwater

Burette ReadingS.No Volume of Boiled Hardwater (VB) Initial Final

Volume of EDTA solution consume(V3)

1 20 ml

2 20 ml

3 20 ml

VB = 20 ml V3 =

V1=

V3 =

Permanent hardness = 1000 X V3

V1

Temporary hardness = 1000 X [(V2-V3)] =V1

Result: The Temporary hardness of the given water sample _________ ppm.

The Permanent hardness of the given water sample ____ _____ ppm.

The Total hardness of the given water sample _____ ____ ppm.



Experiment-2DETERMINATION OF PERCENTAGE OF COPPER IN BRASS

MINERAL ANALYSIS (IODOMETRY)

Aim: To determinate the percentage of Copper present in the given Brass sample using a standardsolution of Potassium Dichromate and Hypo as the link solution.

Apparatus: 100 ml standard flask, Funnel, Burette, Iodometric flask, Conical Flask, 20 ml Pipette & Simple balance with weights,

Chemicals Required: Brass sample,Potassium Dichromate (K2Cr2O7),Hypo (Na2S2O3),Potassium Iodide (KI),6N Conc.HNO3,NaHCO3,6N Sulphuric Acid (H2SO4),Syrupy Phosphoric Acid (H3PO4),

Ammonia solution,Potassiun thiocyanate (KSCN)Starch & distilled water.

Principle:Brass in an alloy which consists mostly of copper (60 to 80 %) and zinc ( 20 to 40% ) along

with small amounts of lead ( 0 to 2% ) , tin ( 0 to 6% ) and iron ( 0 to 1% ).The experiment consists of dissolving a known quantity of brass in nitric acid, removing the

nitrate by fuming with sulfuric acid, adjusting the pH by ammonium hydroxide, complexion the ironpresent using phosphoric acid, and finally titrating the copper ions with hypo by the iodo-metricmethod.

When the brass sample is dissolved in nitric acid, the copper present is brought into solution inthe form of cupric ions. At the same time, tin is converted to meta-stannic acid(SnO2.4H2O ), lead and zinc are oxidized to their respective soluble divalent ions, while iron isconverted to ferric ions. During the treatment with sulfuric acid, nitrate is eliminated, the meta-stannicacid is re-dissolved and lead ions are precipitated as PbSO4 while all other metals go into solution astheir respective sulfates. Out of all the metal ions present in solution, only Cu2+ and Fe3+ are reducibleby iodide. The interference by iron is eliminated by titrimetrically determined by the iodometricmethod.

Chemical reactions:2Cu2

+ + 4I- 2CuI + I2

2S2O3 + I2 S4O6- + 2I-

Cu = I = S2O3-



Procedure:

1. Preparation of standard potassium dichromate:Weigh out accurately about 0.490 gm or 490 mg of the given pure crystalline sample of

potassium dichromate and transfer into 100 ml standard (volumetric) flask. Dissolve thedichromate in a small quantity of distilled water, and make upto the mark. Calculate thenormality of potassium dichromate.

2. Standardization of sodium thiosulphate:Rinse the burette and fill it up with hypo. Pipette out 20 ml of potassium dichromate solution

and then transfer in to the conical flask and add 2 gm/spatula of sodium bicarbonate followed by2 ml of concentrate HCl. Add 10 ml of 10%KI solution. Shake it well, stopper it, and keep it indark place for 5 minutes. Titrate the liberate iodine by running down hypo from the burette withconstant stirring upto 5 ml. When the solution attains a pale yellow colour add 2 ml of freshlyprepared starch solution. The colour changes to blue. Continue the titration drop-wise till thecolour changes from blue to light green indicating the end point.

3. Estimation of copper:About 0.25 g or 250 mg of clean and dry brass sample is accurately weighed and

transferred into a conical flask. Add bout 10ml of 6 N HNO3 and the flask is gently heateduntil the brass sample is completely dissolved. Then 10ml of conc. H2SO4 added and thesolution is evaporated on a sand bath to copious white fumes. The mixture is then allowed tocool and 20ml of water very carefully add from the sides of the flask, in installments of 1mlat a time while cooling under a tap. Boil the solution for 2 minutes and cool. Add liquorammonia drop-wise while shaking the flask vigorously until the appearance of blue cupricammonium complex. Now, 6N H2SO4 is slowly added drop wise until the dark Blue colourdisaapears. Then add 2 ml of syrupy phosphoric acid. The solution is cooled and transferredto a 100ml volumetric flask. The volume is made up to the 100ml mark using distilled water.20 ml of this solution is pipette out into a 150ml conical flask and add about 1 g of solid (KI)potassium iodide. The flask is shaken and the solution is immediately titrated with standardsodium thio-sulphate solution until the solution assumes a faint yellow colour of iodine.About 1 ml of 1% starch solution are added and the titration is continued until the blue colourbegins to fade. At this stage, about 0.5g or 500 mg of potassium thiocyanate (KCNS) isadded and the titration is continued until the blue colour just disappears. The titration isrepeated twice with fresh 25ml portions of the solution to confirm the titer value.

4. Weight of Brass Sample (B):

W1 = Weight of bottle + Brass sample = ____________ gms


Weight of Brass Sample = B = (W1-W2) = ____________ gms.

Weight of the Brass Sample = B =



5. Preparation of Standard (K2Cr2O7)solution:




Normality of the solution = (W1-W2) X 10__ = (W1-W2) X 10 = Equivalent Weight 49

Standardization of sodium thiosulphate:

Burette ReadingS.No Volume of standard(K2Cr2O7)solution (V1)

Initial Final

Volume ofconsume (V2)

1 20 ml

2 20 ml

3 20 ml

V1 = V2 =

N1 = Normality of Potassium dichromate =

V1 = volume of Potassium dichromate = 20 ml

N2 = Normality of Hypo =?

V2 = Volume of Hypo =

N1V1 = N2V2

N2 = N1V1 =V2

N2 = Normality of Hypo =



ESTIMATION COPPER:

Burette ReadingS.No Volume of Coppersolution (V3)

Initial Final

Volume ofconsume (V4)

1 20 ml

2 20 ml

3 20 ml

V3 = 20 ml V4 =

N3= Normality of Copper solution = ?

V3 = volume of Copper Solution = 20 ml

N4 = Normality of Hypo =

V4 = Volume of Hypo =

N3V3 = N4V4

Normality of Copper solution = N3= N4V4

V3

The amount of copper present in the solution can be calculated on the basis that

1ml of 1N Na2S2O3 = 0.06354 g of Cu.

Amount of Copper present in the whole of the given solution (100 ml) = Z = N3 X 63.54 X 1000100

Weight of the Brass Sample = B =

Percentage of Cu in the brass sample : (% of Cu in brass) = Z X 100 =B

Result: Percentage of Copper present in the whole of the given Brass sample(100 ml) = ______ %.



Experiment-3ESTIMATION OF MANGANESE DIOXIDE IN PYROLUSITE.

MINERAL ANALYSISAim: To estimate the amount of MnO2 present in the given sample and hence percentage purity ofPyrolusite.

Apparatus: 100 ml standard flask,Burette,Conical Flask,20 ml Pipette,Funnel,Simple balance with weights,Heating equipment.

Chemicals Required: Pyrolusite, 4N Sulphuric acid (H2SO4),0.1 N Di Sodium oxalate solution,Potassium permanganate (KMnO4),Distilled water.

Principle:The MnO2 present in the pyrolusite sample is reduced by a known excess of standard sodium

oxalate in acid medium. The unreacted sodium oxalate is titrated against a standard KMnO4, until palepink coloured end point is obtained.

MnO2 + H2SO4 + H2C2O4 2CO2 + 2H2O + MnSO4

1ml of 1N KMnO4 = 1 ml of 1N Na2C2O4 = 0.04346 gm of MnO2 = 0.01099 gm of Mn

1 ml of 1N KMnO4 = 1 ml of 1N As2O3 = 0.04346 gm of MnO2

Preparation of Standard Di-Sodium Oxalate solution:Weigh accurately 0.67 gm of Di-Sodium Oxalate and transfer into 100 ml standard flask

through a funnel. Dissolve the compounds small amount of distilled water and make up to the markwith distilled water. Shake the flask vigorously for uniform standard Di-Sodium Oxalate solution.

Standardization of KMnO4 solution:Take 20 ml of the 0.1N sodium oxalate solution in a conical flask; add 50 ml of 4N H2SO4

solution. Titrate with the KMnO4 solution at room temperature until the faint pink colour appears.Warm the solution to 60 to 700 C and continue the titration to a faint permanent pink colour.

Estimation of MnO2:Weigh out accurately about 0.1 gm or 100 mg of the given powdered pyrolusite sample into a

clean dry conical flask and add 50 ml of standard sodium oxalate solution and add 50 ml of 4N(H2SO4) sulphuric acid, put a small funnel into the mouth of the conical flask. Heat with small flametill particles are MnO2 disappear in the conical flask. Rinse the funnel with distilled water into theconical flask, titrate the hot solution, containing the unreacted sodium oxalate with standard KMnO4

solution till there is a pale pink colour.Result: Percentage purity of the given sample of Pyrolusite =



Preparation of Standard sodium oxalate solution:




Normality of the solution = (W1-W2) X 10 = __________X 10 Equivalent Weight 67

Standardization of KMnO4 solution:Burette ReadingS.No Volume of standard

di sodium oxalatesolution (V1 ) Initial Final

Volume ofKMnO4consume (V2)

1 20 ml

2 20 ml

3 20 ml

V1= 20 ml V2 =

N1 = Normality of di sodium oxalate =

V1 = volume of di sodium oxalate = 20 ml

N2 = Normality of KMnO4 =?

V2 = Volume of KMnO4 =

N1V1 = N2V2

N2 = N1V1 = V2

N2 = Normality of KMnO4 =



Weight Of the Pyrolusite Sample:

W1 = Weight of bottle + Pyrolusite = ____________ gms


Weight of Pyrolusite = (W1-W2) = ____________ gms.

Burette ReadingS.No Volume of standardsolution

Initial Final

Volume of consume(V)

1 50 ml

2 50 ml

3 50 ml

V =

Calculations:

Weight of the Ore taken =

Volume of 0.1N Di sodium oxalate solution added in the experiment = 50 ml

Volume of 0.1N KMnO4 run down = V =

Volume of 0.1N KMnO4 consumed = (50 – V) =

1 ml of 1N KMnO4 = 1N Na2C2O2 = 0.04346 g of MnO2

Percentage of MnO2 = (50 - V) X Normality of KMnO4 X 0.04346 X 100 Weight of the sample

Result: Percentage purity of the given sample of Pyrolusite =



Experiment-4

DETERMINATION OF FERRIC IRON IN CEMENT BY COLORIMETRIC METHOD

(Colorimetric Estimation)

Aim: To estimate the amount of Iron (Ferric) present in a sample of cement by calorimetrically usingammonium thiocyanate as a reagent.

Apparatus: 250 ml beaker,Glass rod,Watch glass,100 ml standard flask,Burette,10 ml Pipette,Simple balance with weightsColori-meter,Heating-equipment.

Chemicals Required: Cement sample,Conc. Nitric acid (HNO3),Hydrochloric acid (HCl)Ammonium thio-cyanate &Distilled-water.

Principle:Ammonium thio-cyanate yields a blood red colour with ferric iron and the colour produced is

stable in nitric acid medium. Its optical density is measured in a photo colorimeter and theconcentration of ferric iron is found from a standard calibration curve.

Procedure:

1. Dissolution of the sample:

Weight out accurately about 0.1 gram or 100mg of the cement sample into a clean 100 mlbeaker add about 5 ml of water to moisten the sample, add about 5 ml conc. Hydrochloric acid(HCl) drop-wise and heat the solution till the sample dissolved. Keep the beaker on a small flameand evaporate the solution to almost dryness to expel the excess acid.

Take the beaker out of the flame and add about 20 ml distilled H2O to dissolve the contents.Transfer the solution into 100 ml standard flask. Wash the beaker twice with small portions ofdistilled water, and add the washings to the standard flask. Make up the solution to 100 ml withdistilled water. Shake the flask well uniform concentration.



2. Development of Colour:

Pipette out 10 ml of the solution prepared above, into a 100 ml standard flask; add 1 ml ofconc. Nitric acid (HNO3) and 5 ml of 40% ammonium thiocyanate. Make up the solution to 100 mlwith distilled water and shake the flask well for uniform concentration. Find out the optical densityof the solution using the photo colorimeter and the concentration of the ferric iron from thecalibration curve.

Result: Percentage of Ferric iron present in the cement sample =

Weight of the sample:

W1 = Weight of bottle + sample = ____________ gms


Weight of sample = (W1-W2) = ____________ gms. = ___________ mg

Standard value for calibration curve

Concentration in Milligrams O. D

0.01 0.03

0.02 0.05

0.03 0.07

0.04 0.09

0.05 0.11

0.06 0.13

0.07 0.15

0.08 0.17

0.09 0.19

0.10 0.22

0.11 0.24

0.12 0.26



0.13 0.28

0.14 0.30

0.15 0.32

0.16 0.34

0.17 0.35

0.18 0.37

0.19 0.39

0.20 0.40

0.21 0.42

0.22 0.44

0.23 0.46

0.24 0.48

0.25 0.50

0.30 0.62

0.35 0.70

0.40 0.80

Optical density of given sample solution = O.D =

Corresponding amount of ferric iron from the calibration curve = X = ________ mg.

Calculation:

Percentage of Fe3+ present in the given cement sample = X x 10 x 100 (W1 – W2) mg

Result: Percentage of Ferric iron present in the cement sample =



Experiment-5CONDUCTOMETRIC TITRATION OF STRONG ACID Vs STRONG BASE

(CONDUCTOMETRY)Aim: To estimate the amount of HCl present in given solution.

Apparatus:Conductivity meter,Conductivity cell,Burette,Pipettes,Beakers &Stirrer.

Chemicals Required:

Pure sample of Oxalic acid,0.02M HCl and0.1M NaOH.

Theory:Electrolytic conductivity is a measure of the ability of a solution to carry electric current.

Solutions of electrolytes conduct electric current by the migration of ions under the influence ofapplied field. Like metallic conductors they obey ohms law. At a given temperature the conductivitydepends upon the concentration of the electrolyte.

Conductivity cell:

The electrolytic conductance of an electrolyte is measured in conductivity cells, which arespecially designed. These are available in various sizes and shapes consisting of 2 electrodes. Eachelectrode is a pH disc or plate coated with finely divided Pt black. The electrode is welded to a Pt wirewhich is fused to a glass tube. The glass tubes are firmly fixed in the cell so that the distance betweenthe electrodes would not change during the experiment. The cell is open at one end; the electrolytewhose conductivity is to be measured is dissolved in water and is taken in a beaker. The conductivitycell is placed in the solution and is connected to the conductometer.

Cell constant X:

X of a conductivity cell is the ratio of distance between the 2 electrodes and the exposed areaof one of the electrodes.

X = 1 a

Specific conductance:It is the conductance of ions present in one cubic centimeter of the solution. If the cell constant

of a conductivity cell is 1.0 the measured conductivity of an electrolyte is its specific conductivity. Thecell constant of a conductivity cell is seldom 1.0 cm-1, also measuring ‘l ‘and ‘a ‘are troublesome.Hence the given cell is calibrated for its cell constant, with the help of an electrolytic solutionnormally, a standard KCl whose specific conductivity is known.

Cell constant = known specific conductance / measured conductance



Principle:

The electrical conductance of an electrolytic solution is proportional to a) the ionicconcentration i.e. number of ions present in the solution and b) the ionic mobilies. The ionic motilitiesin aqueous solutions are generally of the order of 6.0 x 10-4 cm2, sec-1 volt-1. But the ionic mobilitiesof H+ and OH- are abnormally high, H+ = 36.3 x 10-4 and OH- = 20.5 x 10-4 cm2 sec-1 volt-1. Thus theconductance of an electrolyte is quite sensitive to concentration of H+ and OH- ions.

Titration of strong acid HCl with strong base NaOH:

In solution HCl is completely ionized. The mobility of H+ ions is high; hence the conductanceof HCl solution will also be high. As NaOH is added to HCl, the fast moving H+ ions are removed byOH- ions of the base as water.

H3O+ + OH- = 2H2O

In solution water is little ionised and Na+ added are slow moving compared to H+ ions of acid. Henceas the titration proceeds, the conductance of titrand HCl decreases gradually till the equivalent point isreached. At the equivalence point the conductance of the solution will be the minimum addition of thebase beyond end point adds Na+ and fast moving OH- ions, resulting in a gradual increase inconductance.

PROCEDURE:Preparation of Standard Oxalic acid solution:

Weigh accurately 0.630 gm or 630 mg of Oxalic acid and transfer into 100 ml standard flaskthrough a funnel. Dissolve the compounds small amount of distilled water and make up to the markwith distilled water. Shake the flask vigorously for uniform standard Oxalic acid solution.

Standardization of NaOH solution:

Pipette out 20 ml of prepared NaOH solution in a conical flask. Add 1-2 drops of methylorange indicator and titrate against standard oxalic acid solution.

Determination of Cell constant:

Take a conductivity cell and determine its cell constant using a 0.1 N KCl solution.

Conduct metric titration:The burette is rinsed and filled with 0.1 M NaOH, 40 ml of given acid is placed in a 100 ml

beaker. The cell is washed with conductivity water which is placed in HCl solution and see that theelectrodes of cell are completely immersed in the solution. The cell is fixed in a cell holder and isconnected to the conductivity bridge. The conductance of HCl solution is noted at a time when 1 ml ofNaOH from the burette is added into HCl solution. After each addition the solution is stirred gentlywith a glass rod and the conductance of HCl is noted. The titration is continued till 20 to 25 ml ofNaOH is added.

Graph:Plot a graph between the conductances measured on Y-Axis and volume of alkali added (X-

Axis) we get a V shaped graph the point of intersecting will be the End-Point of titration and willdetermines the volume of alkali required for neutralization of the acid.



CALCULATIONS:Preparation of Standard Oxalic acid solution:




Normality of the solution = (W1-W2) X 10 = __________X 10 Equivalent Weight 63.03


Burette ReadingS.No Volume of standard oxalic acidsolution (V1 )

Initial Final

Volume of NaOHconsume (V2)

1 20 ml

2 20 ml

3 20ml

V1= V2 =

N1 = Normality of Oxalic acid =

V1 = volume of Oxalic acid = 20 ml

N2 = Normality of NaOH =?

V2 = Volume of NaOH =

N1V1 = N2V2

N2 = N1V1 = V2

N2 = Normality of NaOH =



S.No Volume of NaOH solution added (ml) Conductivity of the solution (ohm-1)1 0.0

2 1.03 2.0

4 3.05 4.0

6 5.0

7 6.08 7.0

9 8.010 9.0

11 10.012 11.0

13 12.014 13.0

15 14.016 15.0

17 16.018 17.0

19 18.020 19.0

21 20.022 21.0

23 22.0

24 23.025 24.0

26 25.0



Volume of the Hydrochloric acid (HCl) used = 40 ml

Volume of NaOH required to reach Equivalent Point = V =

Normality of NaOH =

Strength of HCl = End point titer valve (V) X Normality of NaOH = Volume of HCl used

Result: The strength of HCl calculated is __________ N.



Experiment-6TITRATION OF STRONG ACID VS STRONG BASE BY POTENTIOMETRY

(POTENTIOMETRY)Aim: To estimate the amount of HCl present in given solution.

Apparatus: Saturated calomel electrode,Platinum electrode,Quinhydrone electrode,Potentiometer,Salt bridge,Burette,Pipette,Beakers & glass rod etc.

Chemicals Required: Pure sample of Oxalic acid,0.1M HCl and 0.1M NaOH.

Principle:Quinhydrone (Q) is an equi-molar mixture of quinine C6H4O2 and Hydroquinone C6H4(OH)2.

In acidic medium the following redox equilibrium is established.

Q +2H+ + 2e- ↔ QH2

A pinch of quinhydrone added to an acid solution and a Pt wire or foil dipped in it constitutes a halfcell such electrodes are called indicator electrodes. This is coupled with a reference electrode througha salt bridge making it an electrochemical cell.

Ex: (-)saturated calomel electrode / salt bridge / Qunihydrone + Acid solution / Pt +(or)

(-) Pt, Hg / Hg2Cl2 (s) / KCl (saturated) // H+ , QH2, Q/Pt (+)CELL REACTION:

2 Hg(s) + Q + 2Cl-(aq) ↔ Hg2Cl2(s) + QH2

Ecell = Eright – Eleft in terms of reduction potentials

Ecell = EQE – 0.242 ---------(1)

The left hand half cell is fixed i.e., its potential is constant. Now the right hand half cells potentialdepends on H+ activity. The fundamental equation governing the effect of activity of the ions on thevoltage of an electrode or a cell is Nernst equation given by

Ecell = Ecell - (RT / nF ) lnk

Where k is equilibrium constant of a general reaction aA + bB ↔ cC + dD

The potential will be EQE + nE0QE – (RT /2F ) ln (QH2) / (Q) (H+)2

EQE = E0QE + 0.0591 log (H+) – 0.242

Ecell = 0.458 – 0.0591 pH



During the titration, against and alkali, H+ ion concentration in the half cell containing QH2

will decrease correspondingly the Ecell decreases. The emf will change slowly in the beginning however at the end point relatively higher potential difference will be obtained and then again it willchange slowly. After the end point 5 or 6ml more of the bas is added, quickly and EMF is recorded.Repetition of titration is done by adding 0.2ml of Na OH at a time near the end point. A graph isplotted between EMF and volume of base added. The point of inflection where the graph changes itsdirection is the end point. A differential plot of (E/V) against V* give s a curve whose peakindicates equivalent point.

PROCEDURE:

Preparation of Standard Oxalic acid solution:

Weigh accurately 0.630 gm or 630 mg of Oxalic acid and transfer into 100 ml standard flaskthrough a funnel. Dissolve the compounds small amount of distilled water and make up to the markwith distilled water. Shake the flask vigorously for uniform standard Oxalic acid solution.


Pipette out 20 ml of prepared NaOH solution in a conical flask. Add 1-2 drops of methylorange indicator and titrate against standard oxalic acid solution.

INSTRUMENTATION PROCEDURE:

1) Calibrate the instrument before starting the experiment.2) Take 20 ml of acid solution in a 100 ml beaker and immerse the pH electrode in to the solution.3) Firist carry out the rough titrations by adding 1 ml of NaOH and measure the EMF at each

stage.4) After finding the range of end point, then take fresh sample of acid solutions in a beaker and

carry our the titrations repeatedly by adding 5 ml, 3ml, 2ml, 0.5ml, 0.2ml and 0.1mlsuccessively.

5) After the end point, the volume of alkaline added is increased to 1 or 2 ml. Near the end pointsmaller addition should be added by micro burette.

6) Plot pH values or EMF values against the volume of NaOH added. Draw a smooth curve, thepoint of intersection gives the equivalence point.

7) Plot another graph between E / V values against the titre readings abscissa. The maximumof the curve represents the equivalence point.

Graph:Plot a graph between cell EMF on Y-Axis and Volume of NaOH on X-Axis. For getting the

exact neutralization point another graph drawn E/V Vs Volume of NaOH from this graph thevolume required for neutralization is known.



Preparation of Standard Oxalic acid solution:




Normality of the solution = (W1-W2) X 10 = __________X 10 Equivalent Weight 63.03


Burette ReadingS.No Volume of standardoxalic acid solution(V1 ) Initial Final

Volume of NaOHconsume (V2)

1 20 ml

2 20 ml

3 20 ml

V1= 20 ml V2 =

N1 = Normality of Oxalic acid =

V1 = volume of Oxalic acid = 20 ml

N2 = Normality of NaOH =?

V2 = Volume of NaOH =

N1V1 = N2V2

N2 = N1V1 = V2

N2 = Normality of NaOH =



TABULER FORM:S.No Volume of NaOH

(ml)EMF value (mv) E V E/V

1 02 13 24 35 4

6 5

7 6

8 7

9 8

10 911 1012 1113 1214 1315 1416 1517 1618 1719 1820 1921 2022 2123 2224 2325 2426 25

Volume of NaOH (Eqv.point) =

Normality of NaOH = N2 =

Volume of HCl taken =

Normality of HCl = volume of NaOH (Eqv.point) X Normality of NaOHVolume of HCl taken

RESULT: the normality of HCl by titrating with NaOH using potentiometer is ________ N .



Experiment-7

DETERMINATION OF VISCOSITY OF SAMPLE OIL BY REDWOOD VISCOMETER.

OBJECTIVE:-1. To determine the Absolute and Kinematic Viscosities of a given sample of oil at various

temperatures starting from room temperature.2. To draw the following graphs.

Absolute viscosity Vs Temperature. Kinematics Viscosity Vs Temperature.

APPARATUS:-Red wood Viscometer-I,Thermometers 2No. (0--1100),Stop watch,Measuring flask (50ml),Energy regulator and sample oil.

THEORY:-Viscosity is one of the important properties of a lubricant, which helps in selection of

oils for their suitability for lubricating purposes. A lubricant when used is aimed at reducing frictionbetween different moving parts of a machine by avoiding direct metal-to-metal contact. The thin filmof oil, formed between the moving surfaces, keeps them apart and thus the frictional resistance isentirely on account of the shearing of the liquid. The viscosity of the fluid measures the amount of theinternal friction.

The objective of this experiment is determining the viscosities, therefore, is to ascertainwhether the oil is sufficiently viscous, under the high pressure and temperature conditions of themachine, to adhere to the bearing. The variation of viscosity with temperature is of great importance tothe engineer in all problems of fluid flow and fluid friction and also in pumps, fans and all types ofbearings.

Absolute Viscosity:-It is the shear force required to move a layer of the oil of one-centimeter thickness over

an area of one square centimeter thickness. In C.G.S system it is expressed in poise and in SI system itis expressed in 1N-Sec/m2

1N-Sec/m2 = 10 poise; dyne-sec/cm2=poise

Kinematic Viscosity:-The ratio of Absolute Viscosity to the density is called Kinematic Viscosity. In C.G.S

system it is expressed in Stokes and in SI system it is expressed in m2/sec1m2/sec = 104 stokes; stoke = cm2/sec

Effect of temperature on Viscosity:Increase in temperature causes a decrease in the viscosity of a liquid; where as viscosity

of gases increase with temperature the viscous forces in a fluid are the outcome of inter molecularcohesion and molecular momentum transfer. In liquids the molecules are comparatively more closelypacked, molecular activity is rather small and so the viscosity is primarily due to molecular cohesion.



Since the rate, at which a fluid will flow through an aperture, increase as the internal friction ofthe fluid decreases, the rate of flow through an orifice or short tube may be used as a means formeasuring viscosity. This is the principal involved in Redwood Viscometer-I, which is used in UnitedKingdom for measuring viscosity. The time in seconds required for 50ml of oil to gravitate through theRedwood Viscometer at a given temperature is expressed as its viscosity in Redwood seconds at thattemperature. The Kinematic and Absolute viscosities can be determined from Redwood seconds byusing the following formulae

Kinematic Viscosity (υ) = At – B/t

Absolute Viscosity (µ) = υ.ρ

Where A and B are constants, t is Redwood seconds and ρ is the density of the fluid.

Redwood Viscometer-I is used for determining the viscosity for low viscosity oils. It has anorifice of diameter 1.62 mm with a length of jet of 10mm. The values of A and B for RedwoodViscometer-I are as follows

Viscosity range in R.Iseconds

A B

40-85 0. 264 190

85 to 2000 0. 247 65

DESCRIPTION OF APPARATUS:The Redwood Viscometer consists of a heavily silver plated oil cup with a dish

shaped bottom with a standard hole in hemispherical seating. A spherical ball valve is placed to closethe orifice. The oil cup is surrounded by a bright chrome plated water bath. The water bath is mountedon a stand with leveling screws. The level to which the oil is to be filled into the cup is given by anindex fixed to the inside wall of the oil cup. A standard size stainless steel jet is fitted at the center ofthe bottom of the cup for the flow of oil to be measured. The cylindrical water bath is provided with atap for emptying. The water bath surrounding the oil cup provided with three vanes, having their upperand lower positions rotated in opposite directions to facilitate stirring, which is carried out manually.

For ascertaining the level of equipment a flat circular spirit level is used. Theflow of oil is regulated by the ball value.

The oil cup cover is fitted with an insulated handle, and has suitablearrangement to facilitate thermometer and value rod. The circular spirit level is mounted on a plate tofit on the upper end of the oil cup.

PROCEDURE:-i. Clean the oil cup and dry it. Examine the jet and ensure that it is clean and not obstructed.ii. Mount the bath on the stand and level it with the help of spirit level and leveling screws.iii. Fill the water bath with water until the heating element is below the water surface. Fill the oil

cup with oil up to the mark.iv. Fix the thermometers in the provided space intended for measuring water and oil temperatures.v. Press the connector to the water bath heater pin and the three-pin plug to the plugged to the

socket of the energy regulator box. The three-pin plug from the energy regulator is connected



to the socket of the main supply. Keep the energy regulator knob at the eighty marks andswitch ON the main supply.

vi. Water gets heated and the water temperature reaches 600C stir them well and ensure that thewater and oil temperature are nearly equal.

vii. Place the clear dry 50ml receiving flask centrally below the jet with the top of the neck a fewmm from the bottom of the jet. Open the orifice by lifting the ball valve and note the timetaken for the collection of 50ml oil with the help of stop watch. Note down the time taken isseconds for the oil to get filled in the flask up to the red mark also note down the water and oiltemperature repeat the procedure for various temperatures using the same oil and tabulate thereadings.

OBSERVATIONS:-

Type of oil used:

Calculation of Density:S.NO Weight of the empty jar

W1 gWeight of thejar with fluidW2 g

Volume of thejar in cc

Net weight offluid

W= W2- W1 g

Density =W/V g/cc

1

2

3

4

5



Temperature in 0CS.No

Water Oil

Density of oil(g/cc)

Time takenin Sec.

KineticViscosity inStokes

AbsoluteViscosity inpoise

1

2

3

4

5

SAMPLE CALCULATIONS:-

The values obtained are

Temperature of the oil =

Density () of the oil =

Time for filling the 50ml of the oil =

Then Kinematic Viscosity (υ) = At – B/t centistokes

Where A & B are viscometer containsA = 0.26,B= 171.5,t = time in seconds for collection of 50 ml of oil in the flask

The Absolute Viscosity = kinematic viscosity X Density =

RESULT: The Absolute Viscosity = ___________________in centipoises



Experiment-8DETERMINATION OF SURFACE TENSION

Aim: To determine the effect if soap and detergent on the surface tension of water using aStalagmometer

Apparatus:1. Stalagmometer2. Volumetric flask3. Small rubber tubing4. Screw type pinch cock

Chemicals:1. Detergent solution2. Soap solution

Principle:The size of the drop falling off from the end of tube depends on the surface tension of the

liquid and the size of the capillary end, which provides the line of attachment for the drop. Thus whena liquid is allowed to flow through a capillaty tube, a drop will increase in size to a certain point andthen fall off. The total surface tension supporting the drop is 2r where r is the radius of the outercircumference of the dropping end of the capillary tube. It is along this line that liquid, glass and airmeet and the force acting along the circumference, hence W = 2r, where W is the weight of the dropand 2r is the circumference of the external wall of the capillary tube. The surface tension of the liquidcan therefore be determined from the weight of a single drop and the external radius of the droppingtube.If we have two liquids such thatW1 = 2r1 andW2 = 2r2

then W1/W2 = 1/2

Thus the drop weight method can be employed for comparing the surface tension of twodifferent liquids. However, it is easier to count the number of drops formed by equal volumes to twoliquids than finding the weight of a single drop. For two different liquids, the weights of equalvolumes are proportional to their densities. Let N1 and N2 be the number of drops of liquid producedfrom the same volume V of the two liquids.

Volume of a single drop = V / N1

Weight of a single drop = (V / N1) d1 or 2r1 = (V / N1) d1

Similarly for liquid 2

2 r2 = (V / N2) d2

Where d1 and d2 are the densities of the respective liquids. Dividing these two equations we get1 / 2 = (N2.d1) / (N1.d2)



Procedure: Take a clean and dry Stalagmometer Attach rubber tubing with a screw pinch cock to the upper end of the stalagmometer to control

the flow of the liquid and clamp it to a stand. Make marks above and below the bulb with a marker pen if it is not marked. With the help of the rubber tubing, suck distilled water into the stalagmometer till the level

rises above the upper mark. Now allow the liquid to flow through the capillary (control the flow rate using the crew pinch

cock) and count the number of drops formed (N1) till the liquid level reaches the mark belowthe bulb.

Dilute the given stock soap solution ( 1%) to appropriate dilutions as given below using aburette and determine the number or drops for each of these concentrations. Tabulate the data.

Repeat the above procedure for 0.5, 0.1 and 0.05 % of detergent solution also and tabulate it asabove.

SNo Volume of water

+ Volume of

soap/detergent

solution (ml)

Concentration

of

soap/detergent

solution

Exp.1 Exp.2 Average

(N)

Surface

tension

(dynes/cm)

1 50 + 0 Pure water

2 25 + 25 0.5 %

3 45 + 5 0.1 %

4 47.5 + 2.5 0.05 %

Calculations: Surface tension of water at 25°C = 72 dynes / cm

r1 = Surface tension of the reference liquid (i.e., water)

r2 = Surface tension of the test liquid

r1 = N2.d1

r2 N1.d2

Result : The surface tension of the given liquid = ……….dynes / cm

Precautions: Number of drops per minute must be in between 15-20 The lower end of stalagmometer should be free from grease hence wash the stalagmometer first with

benzene or NaOH and then with chromic acid. Stalagmometer should be kept in a vertical position.



Experiment-9IDENTIFICATION OF FUNCTIONAL GROUPS PRESENT IN ORGANIC COMPOUNDS

S.No Experiment Observation InferenceI PRIMARY TESTS:

a) State Solid /LiquidColourless liquid Aldehydes, ketones may be present

Yellow coloured liquid Nitro compound may be present

Colourless solid Acids, amides, anilides, carbohydrates maybe present

b)Colour

Brown (or) dark colouredsolid (or) liquid

Phenols, aromatic amines may be present

Pleasant Nitro compounds may be presentPhenolic Phenols may be present

Acidic acidic compound may be present

Aniline like smell Aromatic amines may be present

c)Odour

Oil of bitter almond Nitrobenzene, benzaldhyde may be presentSmoky Aromatic compoundNon-luminous Aliphatic compounds containing low

percentage of carbon

II IGNITION TEST

Charring Compounds such as carbohydrate & itssalts get charred on ignition.

SOLUBILITY:Solubility test: One drop of the liquid or small quantity of the solid is dissolved in the following:

Experiment Observation Inferencea)Ether Insoluble carbohydrate/amide/imide/anilide may be

presentSoluble, solution is neutralto litmus

carbohydrate may be presentb)Water

Solution turns blue litmusred

acidic compound may be present

Soluble with effervescenceand regenerated onacidification with dil.HCl

Carboxylic acid may be present

Slow effervescence Polyhydric Phenols may be present

c)Saturated NaHCO3

solution

Slow effervescence &solution turns Yellow

Nitro phenols may be present

No characteristic change ketones, amines, aromatic nitro compoundsmay be present

III

d)Dilute NaOHsolution (changes inthe cold are observed& heated ifnecessary)

Dissolves readily in thecold & substance isregenerated on addingconc. HCl

Aromatic acids, phenols may be present



Dissolves & solution turnsYellow colour is removedon adding HCl

Nitro phenols, phenolic aldehydes may bepresent

Dissolves readily forming aYellow or brown solutionon boiling

Carbohydrates may be present

Dissolves in cold &solution turns Yellow,Brown & finally dark onshaking

Polyhydric phenols may be present

Ammonia gas is evolvedon boiling

Amides may be present

Oily drops are formed withaniline like odour onboiling

Anilides or Toluidines may be present

Soluble with effervescence carboxylic acid may be presente) Dil. Na2CO3

Soluble withouteffervescence

Phenolic Group may be present

f) Dil. HCl Soluble and regenerates onadding alkali(NaNO2)

Basic compounds like amines may bepresent

Blackening witheffervescence with theevolution of CO and (or)CO2 & SO2

Carbohydrates or certain hydroxyl aliphaticacids like Tartaric acid may be present

Blackening withouteffervescence

Polyhydric Phenols like Resorcinol may bepresent

g) Action of Conc.H2SO4: To a smallamount of organiccompound in a drytest tube add conc.H2SO4 and note thechange in the coldand then warmgently.

CO and CO2 evolved, noBlackening

Oxalates (or) Oxalic acid may be present

Test for Un-saturation

Experiment Observation Inference

De-colorization of bromine Un-saturated compounda) Action ofbromine in CCl4: to1ml of bromine inCCl4, add drop of theliquid or smallquantity of the solid.

No de-colourisation Saturated compound

Decolourisation of KMnO4

with Brown ppt.Unsaturated compoundb)Bayer’s Test:

Add one drop of theliquid or smallamount of the solidto 1 ml of dil.KMnO4

No decolourisation ofKMnO4

Saturated compound

IV

c) Br water: 1 ml ofBromine water add a

Decolourisation Unsaturated compound



drop of Liquid orsmall quantity ofsolid.

No Decolurisation Saturated compound

S.No Ether H2O NaHCO3 NaOH HCl H2SO4 Compound1 + - + + - + Carboxylic acid

2 + - - - + + Base

3 + - - - - - Hydrocarbon

4 - + + + + + Carbohydrate

5 + - - - - + Neutral Compound

FUNCTIONAL GROUP ANALYSISA simple organic compound has one functional group but it may contain two or more

functional groups. All these commonly found functional groups have been divided into four groups.The groups correspond to various elements in the organic compounds and are given below.Type Elements present in compound

organicOrganic compound and its functional group

1. a)C&Hb) C,H& O

HydrocarbonsCarboxylic acid, phenol and alcohol(-OH),aldehyde,ketone, ether and ester

2. a)C,H&Nb)C,H,N& O

AminesAmides, nitro compounds & anilides

3. a)Halogens C,H,& Xb) Halogens and C,O,AX,O

Halogenated hydrocarbonsAcid halides,chloral hydrate.

4. C,H,S,O Sulphonic acid

ELEMENTAL ANALYSISC,H and O are considered as basic elements of organic compounds. Other than these three

elements, the elements that are most commonly present in organic compounds are nitrogen, sulphurand halogens. The presence of these elements is detected by Lassaigne”s test.

Preparation of sodium fusion extract:Heating procedure for liquids: Gently heat a small piece of freshly cut and dried sodium in an

ignition tube in the beginning and then to red hot. Remove the red hot ignition tube from the flame andadd one drop of the liquid. Repeat the heating process again until the tube becomes red hot, removeand add another drop of the liquid. Repeat the operation two or three times.

Heating procedure for solids:Gently heat a small piece of freshly cut and dried sodium in an ignition tube in the beginning

and then to red hot. Remove the red hot ignition tube from the flame and add a few milligrams ofsolid. Repeat the heating process again until the tube becomes red hot. In the case of solids there is noneed to add the compound again.

Take 3 to 4 ml of distilled water in a mortar and immerse the red hot ignition tube into water.Grind the ignition tube to pieces with the pestle, filter. Divide the filtrate into three parts and performthe following experiments.



Compounds containing:C,H,N,O,S, Halogen (X) + Na NaCN + NaOH + Na2S = NaX

Experiment Observation InferenceLassaigne”s Test:Test for Nitrogen: To one portion of sodiumfusion extract add 2 drops of freshly prepared FeSO4 solution.Boil, cool and acidify with dil.H2SO4 with shaking until thesolution is clear. Now add few drops of FeCl3

Bluish / GreenPrecipitate / colourPrussian blue colourNo colour change

NitrogenpresentNitrogenabsent

1) TESTS FOR CARBOXYLIC GROUP (-COOH):

S.NO EXPERIMENT OBSERVATION INFERENCECO2 gas evolved Carboxylic acid may

be present.1. Add 1 ml of saturated sodium

bicarbonate solution to 1 drop of theliquid or small amount of the solid No CO2 is evolved Carboxylic acid

absent.Blue litmus changesto red.

Carboxylic acid maybe present.

2. Dissolve one drop of liquid or smallamount of solid in 1 ml aqueous alcoholand moisten the blue litmus paper

No colour change. Carboxylic acid absent

3. Esterfication: Dissolve one drop ofliquid or small amount of solid in 5 mlof methyl/ethyl alcohol and add 2-3drops of conc. H2SO4 and warm onwater bath and pour the content intoNaHCO3/Na2CO3 sol.

Fruity odour Carboxylic acidpresence is conformed

4. Phenolphthalein Test: Dissolve smallamount of the compound in water /alcohol. add a drop of phenolphthaleinand well diluted NaOH sol. drop wise

Pink colour isobtained

Carboxylic acidpresence is conformed

2) TETS FOR AMINES (-NH2):S.NO EXPERIMENT OBSERVATION INFERENCE1. Carbylamine test: add few drops of

chloroform to about small amount ofthe compound and add 2-3 ml ofethanolic NaOH / KOH mix well andwarm gently.

A foul smell of isocyanide isobserved, by adding conc.HCl smell can be destroyed.

Amine may bepresent

2. Nitrous acid test: take small amountof the given compound is 2 ml of dil.HCl and cool. Now add 10% aqueousNaNO2 sol.

A brisk effervescence isappeared.

Aminepresence isconformed.

3. Diazotization test: dissolve smallamount of the organic compound in 2-3ml dil HCl cool under tap-water nowadd 2 ml of 2.5 % NaNO2 solution, coolagain and add 1ml of alkaline β-naptholsol.

An orange red or a red dye isappeared.

Aminepresence isconformed.



3) TEST FOR HYDROCARBONS(C&H):

S.NO EXPERIMENT OBSERVATION INFERENCE

Red colour is appeared Mono cyclichydrocarbon isconformed.

Blue or violet colour isappeared.

Bicyclic hydrocarbonis conformed.

1. Sublimation test: To small amountof the compound add 3ml ofchloroform and shake well. Thentransfer a pinch of AlCl3 into a drytest tube and sublime them byadding above solution to thesublimed AlCl3 such that thechloroform layer touches the AlCl3.

Green colour is appeared. Poly hydrocarbon isconformed.

4) TEST FOR CARBOHYDRATES:

S.NO EXPERIMENT OBSERVATION INFERENCE

1. Blackening with H2SO4: heat smallamount of the compound in 1ml ofconc. H2SO4 .

Immediately charring andblackening of the solutionis observed.

Carbohydratemay be present

2. 2, 4 DNP test: To small amount ofcompound add 1 ml of water and add 1ml of 2, 4 DNP reagents.

Orange ppt. appears Carbohydratemay be present

3. Molisch test: dissolve small amount ofcompound in 4 ml of water add 3-4drops of alcoholic /-napthol and add2 ml of conc. H2SO4 carefully from thesides of the test tube.

A deep violet coloured isformed at the junction oftwo layers.

Carbohydrate isconformed.



5) TEST FOR CARBONYL COMPOUNDS:

S.NO EXPERIMENT OBSERVATION INFERENCE1. 2,4-DNP test:

To 2-3 drops of compound add 1 ml of the2, 4-DNP reagent. Keep it in hot water bathfor few minutes.

An orange ppt of 2, 4-Dinitro phenylhydrazone is formed.

Carbonylcompound ispresent

2. Schiff’s test:To 1 ml of the compound add 5 ml of theschiffs reagent and heat the mixture on awater bath for 2 minutes.

No purple colour isdeveloped

Aldehyde groupis absent

3. Tollen’s test:To 1 ml of the compound add 5 ml of thetollens reagent and heat the mixture on awater bath for 5 minutes.

No silver mirror isdeposited or no greycolour

Aldehyde groupis absent.

4. Fehlings test:To 1 ml of the compound add 1 ml ofNa2CO3 solution and 1 ml of the Fehlingssolution A and 1 ml of Fehling solution B.Boil the mixture for 2-3 minutes.

No red colour ppt isformed.

Aldehyde groupis absent.

5. Bisulphate test:To 1 ml of the compound add 1 ml ofsaturated Sodium bisulphate solution.

White NaHSO3 productis formed.

Ketone ispresent.



Experiment-10

PREPARATION OF ACETYL SALICYLIC ACID (ASPIRIN)

Aim : Preparation of Acetyl Salicylic Acid (Aspirin) with using salicylic acid.

Apparatus: 250 ml Round bottom Flask, 200 ml beaker,

Glass rod,Funnel,Dropper,Filter papers,Simple balance with weights

Chemicals Required: Salicylic acid, Acetic Anhydride Acetic acid

Conc. Sulphuric Acid (H2SO4) &Distilled-water.

Chemical Reaction:

Procedure:

2.5 gms Salicylic acid and 5 ml Acetic anhydride taken in 200 ml Round Bottom Flask, mixwell, and add 1 or 2 ml Concentrated sulphuric acid . Heat it 50-600C on water bath for 10 to 15minutes. Cool and add 100 ml water and filter the precipitate.

Result:

Yield =

Melting Point =



Experiment-11DETERMINE THE RATE CONSTANT OF

HYDROLYSIS OF METHYL ACETATE

Aim: To determine the order of reaction and rate constant for the acid catalyzed hydrolysis of methylacetate.

chemicals: Methyl acetate,0.5N HCL,0.1NSodiumhydroxide,Phenolphthalein indicator & ice.

Apparatus: Iodination flask 250ml,Burette,pippete10ml,250 ml conical flask.

Principle:Hydrolysis of methyl acetate is catalyzed by HCl. The rate of reaction is followed by titrating the

acetic acid formation during hydrolysis by sodium hydroxide at certain intervals of time.

Procedure: Fill the burette with 0.1N sodium hydroxide solution and fix to the stand. Take 90ml of 1NHCl

into an iodination flask and add 10ml of methyl acetate. Mix thoroughly for 5 to 10 seconds and note time. Immediately pipette out 10ml of the reaction mixture into a clean conical flask containing ice

and phenolphthalein indicator. Titrate it against 0.1N sodium hydroxide. Note the volume of sodium hydroxide required for titration as Vo pour the contents out, clean

the conical flask and keep it ready for next titration by adding cold water and indicator. After 10 mins of time pipette out another 10ml of the reaction mixture into the conical flask

and titrate against sodium hydroxide as before. Note the volume as V10. repeat the titrations at every 10mins of intervals upto 60 mins as V20,V30,V40 ,V50 and V60.heat

the reaction mixture on a water bath at 600c for 30 minutes cool and pipette out 10ml ofreaction mixture into a conical flask, add phenolphthalein indicator and titrate with sodiumhydroxide and note the volume as V

Graph: Plot a graph between Time (t) Vs Log (V-Vt ), Time (t) taken on X-Axis and Log (V-Vt )taken on Y-Axis. Find out the slope, using slope to calculating K.

Result: the hydrolysis of acetic acid is a pseudo first order reaction the experimental value of K =



Vol of NaOHS.NO TIME

Intial Final

V-Vt LogV-Vt

Log V-V0

____V-Vt

K1 = 2.303/t Log V-V0

_______________V-Vt

1

2

3

4

5

6

7



Through Graph: Slope = S = y2-y1 = x2-x1

K = 2.303 X S =

Activation Energy:From the value of the reaction rate constant at two temperatures calculate the energy of

activation for the reaction using the equation:

Log K2 = -- E [ 1/T2 – 1/T1]K1 2.303R

E = T1 T2 X 4.567 X Log K2

T2 - T1 K1

Result: The rate constant of the reaction (k) = ________.

The energy of activation (E) =_____________



Experiment-12ADSORPTION OF CHARCOAL

AIM: To determine the Adsorption of aqueous acetic acid by Activated Charcoal and to studyadsorption isotherm.

APPARATUS: Stopper bottles, 20 ML Pipette,

Burette, Beakers

CHEMICALS: Powdered activated charcoal,0.5N Glacial acetic acid and 0.1 N NaOH.

PRINCIPLE: Freundlich adsorption isotherm is given by the expression:

x = KC 1/n - equation-1m

Where ‘X’ and m are the amounts of solute (adsorbate) and adsorbent respectively, ‘C’ is theequilibrium concentration of adsorbate. ‘K’ is a constant depends on both, the nature of adsorbent aswell as of adsorbate. “n” is another constant and depends only on the nature of adsorbate.

Taking log, the equation (1) can be written as

log x = log k + 1 log Cm n

When log X is plotted against log C, it gives a straight line whose slope is 1 and them n

Intercept log k.

PROCEDURE:Proceed stepwise as follow:1. Take 50, 40, 30, 20 and 10 ml of 0.5 N acetic acid in stopped bottles and to these add 0, 10, 20,

30 and 40 ml of distilled water respectively and label them.2. Transfer 1 gm of activated charcoal to each bottle then shake these vigorously for about one

hour and allow them to stand for half an hour to attain the room temperature.3. Filter off charcoal and while filtering discard initial nearly four ml filtrate in each case.4. Take 5 ml of each filtrate and titrate it against standard solution of 0.1 N NaOH using

phenolphthalein as an indicator.5. Note the reading in each case.

OBSERVATIONS:

1 .room temperature =. . . . . . °C2. Amount of charcoal used in bottle = 1g3. Volume of solution taken for titration each time = 5 ml



BottleNo

Volume of 0.5 NCH3COOH (ml)

Volume ofwater added

Initialnormality of theacid (normality)

C2

Volume ofNaOH used, V

12345

5040302010

010203040

0.500.400.300.200.10

Calculate the normality of the acid after adsorption using N1V1 = N2V2. Subtract this value frominitial normality of the acid. This will give you the normality of the acid adsorbed. Let it be N.

The amount of the acid adsorbed, x = N X 60 gm 1000

m = 1g in all cases

Repeat the calculation of remaining solutions and produce your results in tabular form as below:

Bottlenumber

Initialnormality

acid

Normality ofacid adsorbed

Amount ofacid adsorbed

x

x / m log x / m log C

12345

0.500.400.300.200.10

Plot the graph between x/m and log C. The slope is equivalent to 1 / n and the intercept to log k.

RESULT: The trend of the graph is in accordance with Freundlich adsorption isotherm. The values of1 and ‘k’ are respectively……. and……. n

PRECAUTIONS:1. Shake all the solutions properly and uniformly2. Filter the solution before proceeding for titration and discard the initial small volume of the

filtrate.3. Do not use wet filter paper in filtration as it may dilute the solution.

Eng.chemsitry Labmanual

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