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CHEMISTRY LABORATORY MANUAL (2019-2020)
For
COMMON TO ALL BRANCHES
(CSE, ECE, ME, CIVIL, EEE & IT)
ADITYA INSTITUTE OF TECHNOLOGY AND MANAGEMENT
(AN AUTONOMOUS INSTITUTE)
(Approved by AICTE, Accredited by NBA & NAAC, Recognized Under 2(f), 12(B) by
UGC Permanently Affiliated to JNTUK, Kakinada)
K.KOTTURU, TEKKALI–532201, SRIKAKULAM Dist. (A.P)
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AR-18
Aditya Institute of Technology and Management (Autonomous), Tekkali I Year B. Tech (1st Sem. EEE, CSE & IT and 2nd Sem. ECE, ME & CE)
CHEMISTRY LABORATORY (Common to All Branches)
Subject Code: 18BSL102 Internal Marks: 40 Credits: 1.5 External Marks: 60
Course Objectives:
The students will become familiar and understand about:
Measure molecular/system properties such as kinematic viscosity, acid number of lubricating oil,
etc
Measure molecular/system properties such as surface tension, viscosity, pH, conductance of
solutions, redox potentials, etc
Measure molecular/system properties such as chloride content, hardness of water, dissolved
oxygen, iron by colurimeter etc.
Synthesize a small polymer molecule and analyze a salt sample.
Estimate iron (by colurimeter), partition coefficient, adsorption of acetic acid by charcoal etc.
Course Outcomes:
The students will learn to:
Measure molecular/system properties such as kinematic viscosity, acid number of lubricating oil,
etc.
Measure molecular/system properties such as surface tension, viscosity, pH, conductance of
solutions, redox potentials, etc
Measure molecular/system properties such as chloride content, hardness of water, dissolved
oxygen, iron by colurimeter etc.
Synthesize a small polymer molecule and analyze a salt sample.
Estimate iron (by colurimeter), partition coefficient, adsorption of acetic acid by charcoal etc.
LIST OF EXPERIMENTS: Choice of 10-12 experiments from the following:
1. Determination of surface tension and viscosity
2. Determination of Hardness of water sample by EDTA Method.
3. Conductometric estimation of Acid by Base.
4. Conductometric estimation of mixture of acids by base.
5. Potentiometric Titrations.
6. Synthesis of a polymer/drug.
7. Determination of acid value of an oil
8. Chemical analysis of a salt
9. Determination of Dissolved Oxygen present in the given water sample by Modern Winkler’s
Method
10. Colurimetric estimation of iron
11. pH metric titrations
12. Determination of the partition coefficient of a substance between two immiscible liquids
13. Adsorption of acetic acid by charcoal Use of the capillary viscosimeters to the demonstrate of
the isoelectric point as the pH of minimum viscosity for gelatin sols and/or coagulation of the
white part of egg
14. Thin layer chromatography.
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15. Determination of Chloride content present in given water sample.
16. Determination of kinematic viscosity of given lubricating oil.
TEXT BOOKS:
1. “Practical Engineering Chemistry” by K.Mukkanti, etal. B.S.Publications, Hyderabad (2011).
2. “Lab Manual on Engineering Chemistry” by Sudharani, Dhanpat Rai Publications, Co., New
Delhi., (2009).
REFERENCE BOOKS:
1. “Engineering Chemistry Lab Manual” by Shuchi Tiwari (2010), SCITECH Publications.
2. “Vogel’s Text Book of Quantitative Chemical Analysis”, 6th Edition by G. J. Jeffery, J. Bassett,
J. Mendham, R.C. Denney, Longman Scientific & Technical Publications, New York.
3. “A Text Book of Engineering Chemistry” by R. N. Goyal and H. Goel, Ane Books (P)
Ltd.(2009).
4. “A Text Book on experiments and calculations Engineering” by S.S. Dara, S.Chand & Company
Ltd. (2003).
5. “Instrumental methods of Chemical Analysis”, Gurudeep R, Chatwal Sham, K. Anand, Latest
Edition (2015), Himalaya Publications.
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CYCLE-I EXPERIMENTS
Expt.
No.
Experiment Page
No.
01 Determination Of Dissolved Oxygen Present In The Given
Water Sample By Modern Winkler’s Method.
7
02 Determination Of Acid Number Of Given Lubricating Oil. 11
03 Determination Of Strength Of A Strong Acid By pH Metric
Method.
15
04 Conductometric Determination Of Strength Of An Acid
Using Strong Base.
19
05 Determination Of Total Hardness Of Water Sample By
Using EDTA Method.
23
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Observations & Calculations: Step-1: Standardisation of Sodium thiosulphate soludion: Burette : Sodium thiosulphate solution. Conical flask : Standard K2Cr2O7 + 5% KI + H2SO4 Indicator : 2 ml starch solution End Point : Blue to colourless
S.No. Volume of Potassium
dichromate (ml) Burette readings (ml) Volume of Hypo Rundown
(V ml) Initial Final 1
2
3
4
Potassium dichromate Sodium thiosulphate N1 = N2 = V1 = V2 =
N2 = 2
11
V
VN =
…………….. ------------------ ------------------------N
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EXPERIMENT NO - 1 DETERMINATION OF DISSOLVED OXYGEN IN THE GIVEN WATER SAMPLE
Aim: To find the quantity of Dissolved Oxygen present in given water sample.
Apparatus: BOD Bottles (300ml), Burette, Pipette, Conical Flask, Burette Stand, Wash bottle.
Reagents: 0.02N K2Cr2O7, 48% Manganese Sulphate, Alkali-Iodide-Azide Reagent, Starch
Indicator, Sodium Thiosulphate, Con. Sulphuric Acid, Sodium Hydroxide, sample water, Distilled
water.
Principle:
Step-1: As the thiosulphate is a secondary standard solution, it has to be standardized by
titrating against a primary standard dichromate solution iodometrically using starch indicator.
K2Cr2O7 + 6KI + 7H2SO4 Cr2(SO4)3 + 4K2SO4 + 3I2 + 7H2O
2Na2S2O3 + I2 → Na2S4O6 + 2NaI
Step-2:
Oxygen present in the water sample oxidizes divalent manganese (Mn2+) to its higher oxidation state
(Mn4+) in the presence of Alkali-Iodide-Azide solution. Oxidized manganese liberates iodine from
potassium iodide in acidic medium. The amount of Iodine liberated is equivalent to dissolved oxygen
present in water sample. The liberated iodine is estimated by titrating with 0.025N hypo using starch
as an indicator (wrinkler titration).
OHMnOOOHMn 222212 2
(brown ppt)
222
2 242 IOHMnHIMnO
6423222 22 OSNaNaIOSNaI
(Sodium tetrathionate) Formulas:
The strength of sodium thiosulphate N2 = 2
11
V
VN
The amount of dissolved oxygen in the given water sample = Titre value x conc. of hypo x 8 x 1000 mg/lit. Volume of sample Procedure: Step-1: Standardisation of Sodium thiosulphate (hypo) solution: 1) Fill the burette with sodium thiosulphate solution.
2) Pipette 10ml of standard potassium dichromate solution into Conical Flask. Add 5 ml
of 5 % KI solution and 5 ml of 5N H2SO4 solution.
3) Cover the conical flask with watch glass and put into dark place at 10 min.
4) Titrate the sample solution with thiosulfate until the solution becomes pale yellow.
Introduce 5 drops of starch indicator, and titrate with constant stirring to the
disappearance of the blue colour. Note down the burette reading.
5) Calculate the normality of Sodium thiosulphate.
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Step-2: Determination of Dissolved oxygen in water sample:
Burette : Std. Hypo solution (0.025N)
Concial Flask : 20 ml water sample consists of liberated Iodine
Indicator : 2 ml starch solution
End Point : Blue to colourless.
S.No. Volume of Water sample (ml) Burette readings (ml) Volume of Hypo Rundown
(V3 ml) Initial Final 1
2
3
4
Dissolved oxygen in the given water sample
= V3 x N2 x 8 x 1000 20 = _______________
= ________________
= ___________ mg /litre
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Step-2: Determination of dissolved oxygen present in water sample:
1) Collect 250 ml water sample in a 300ml capacity of BOD bottle.
2) Add 2 ml of manganese sulphate and 2 ml of Alkaline-Iodine-Azide solution.
3) Stopper the BOD bottle immediately.
4) Appearance of brown ppt. indicates the presence of DO.
5) Mix well by inverting the bottle 2 to 3 times and allow the brown ppt. to settle down.
6) Add 2 ml. of conc. H2SO4 solution to dissolve the precipitate.
7) Take 20 ml. of this solution into a clean conical flask.
8) Titrate the liberated iodine with standard hypo solution present in the burette.
9) Add 2 ml of starch solution when the colour of the solution becomes pale yellow. The
solution turns to blue colour.
10) Continue the titration till the blue colour is disappeared.
11) Note the volume of hypo used (V ml)
12) Repeat the titration till the concordant readings are obtained.
13) Calculate the amount of Dissolved Oxygen in the given water sample by using the formula
Result:
Source of water sample Dissolved oxygen (mg/l)
Marks awarded Signature of the faculty
Environmental Significance:
1. The level of dissolved oxygen in fresh water bodies is 8-15 mg/L at 250c
2. If the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets
inhibited.
3. The dissolved oxygen is used by microorganisms to oxidise organic matter
4. Oxygen depletion helps in release of phosphates from bottom sediments and causes
eutrophication.
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Observation and Calculation: Step-1: Standardization of KOH Solution.
Burette : KOH solution
Conical flask : 20 ml. of Oxalic Acid
Indicator : Phenolphthalein
End point : Colourless to pink.
S. No. Vol. of Oxalic Acid
Burette readings Vol. of KOH rundown Initial Final
1
2
3
4
Normality of KOH N2 = 2
11
V
VN
N1 = Normality of oxalic acid
V1 = Volume of the oxalic acid
V2 = Volume of the KOH
N2 = 2
11
V
VN
-----------------------
------------------------ N
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EXPERIMENT NO-2
ACID NUMBER OF LUBRICATING OIL Aim: To determine the Acid number of lubricating oil.
Apparatus: 50 ml burette, 20ml pipette, 250 ml conical flask, 100ml beaker, 250 ml beaker,
50 ml beaker and 50 ml measuring jar.
Chemicals: KOH solution, 0.02N oxalic acid, Oil sample, Phenolphthalein indicator, Ethyl
alcohol.
Principle:
The Acid number of lubricating oil is defined as the number of milligrams of potassium
hydroxide required to neutralize the free acid present in 1 g of the oil sample. In good
lubricating oils, the acid number should be minimum (<0.1). Increase in acid value should be
taken as an indicator of oxidation of the oil which may lead to gum and sludge formation
besides corrosion. Since free fatty acids present in the oil react with base, their quantity can
be estimated by titrating the known weight of the oil sample dissolved in a suitable solvent
with a standard alcoholic solution of KOH to a definite end point
H2C2O4 + 2KOH K2C2O4 + 2 H2O
RCOOH + KOH RCOOK + H2O
Procedure:
Step 1: Standardization of KOH
20 ml standard oxalic acid solution is pipette out into a 250 ml of conical flask and
few drops of Phenolphthalein indicator is added.
The above solution is titrated with standard KOH solution taken in the burette until
the solution changes from colorless to light pink colour
The same procedure is repeated until any two readings coincide
The concentration of KOH is calculated.
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Step-2: Determination of Acid Number:
Burette : Std. KOH solution Conical flask : 1gm. of lubricating oil + 5 ml of alcohol. Indicator : Phenolphthalein End point : Colourless to pink.
S. No. Vol. of
lubricating oil
Burette readings Vol. of KOH
Initial Final
1
2
3
4
Acid Number of given oil sample is
(mg of KOH required to neutralize the acid present in 1 gm of oil) =
1000
100..2 KOHofVolKOHofwtEqN
N2 = Normality of KOH
Eq. wt of KOH = 56.01
Vol. of KOH = titer value in the above titration
=------------------------ = -----------------------
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Step 2: Determination of Acid Number of given oil sample
1 gram (1.1 ml) of oil sample is taken in a 250 ml conical flask and dissolved in 5 ml
of Ethyl alcohol.
One or two drops of Phenolphthalein indicator is added and the solution is titrated
with KOH taken in the burette until the solution changes from colorless to light pink
The same procedure is repeated until any two readings coincide
The Acid Number of oil sample is calculated.
Result: Name of
lubricating oil sample
Weight of oil sample
Acid number Marks awarded Signature of the faculty
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Step-1: Observations & Calculations:
Burette : NaOH Solution
Conical Flask : 20 ml Oxalic Acid
Indicator : Phenolphthalein
End Point : Colour less to Pale pink.
S.No. Volume of Oxalic acid (v1 ml)
Burette readings (ml) Volume of NaOH Rundown (v2 ml) Initial Final
1
2
3
4
Calculations:
Oxalic Acid:
M1 = Molarity of Oxalic Acid = 0.2M
V1 = Volume of Oxalic Acid = 20 ml
n1 = Moles of Oxalic Acid = 1
Sodium Hydroxide:
M2 = Molarity of NaOH =?
V2 = Volume of NaOH =
n2 = Moles of NaOH = 2
Molarity of NaOH =---------------------
=---------------------
=---------------------M
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EXPERIMENT-3 pH METRIC ESTIMATION OF ACID BY BASE
Aim: To determine the Amount of unknown acid solution with standard base solution by pH
metric method.
Apparatus: pH Meter, Glass membrane electrode, 100ml Beaker, Burette, Volumetric Flask,
Glass Rod.
Chemicals: Stock acid solution, 0.2 M oxalic acid and Stock base solution.
Principle: When a glass surface is in contact with a solution it acquires a potential which
depends on H+ ion concentration of solution. This observation which has been made by
Haber is now used as basis of method of determining the pH of a solution where other
electrode cannot be used. The glass electrode has attained much attention in recent years
because it can be used almost in all solutions except those which are strongly acidic or
strongly alkaline. It has been observed that potential difference exists at the interface between
glass and solution containing H+ ions. The magnitude of the difference of potential for a
given variety of glass varies with its ions concentration at 250C given by:
E = E0 + 0.0591 log [H+]; E0 = A constant for the given glass electrode.
H2C2O4 + 2 NaOH Na2C2O4 + 2H2O HCl + NaOH NaCl + H2O
Formula:
Procedure:
Step 1: Standardization of sodium hydroxide by using oxalic acid
1. Rinse and fill the burette with the given NaOH solution
2. Pipette out 20 ml of 0.2 M oxalic acid solution into a clean conical flask
3. Add 1 or 2 drops of phenolphthalein indicator to oxalic acid solution.
4. Titrate the solution against sodium hydroxide solution drop wise with shaking till the
solution changes to pale pin
5. Note the volume of NaOH used. It is the end point
6. Repeat the titration until the concordant readings are obtained
7. Calculate the molarity of NaOH by using the formula mentioned above
Step 2: Determination of molarity of unknown HCl by using standard NaOH through
pH metric titration
1. Rinse and fill the burette with standard NaOH solution
2. Now you collect unknown acid in 100 ml volumetric flak and makeup with distilled
water
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Step-2: Observations and Calculations: pH Metric titration in between HCl and NaOH
Volume of NaOH Added pH Volume of NaOH Added pH 0 5.5
0.5 6.0 1.0 6.5 1.5 7.0 2.0 7.5 2.5 8.0 3.5 8.5 4.0 9.0 4.5 9.5 5.0 10.0
Calculation of unknown molarity of HCl solution:
Sodium Hydroxide:
M2 = Molarity of NaOH =
V2 = Volume of NaOH =
n2 = Moles of NaOH = 1
HCl:
M3= Molarity of HCl =?
V3= Volume of HCl = 10 ml
n3 = Moles of HCl = 1
Molarity of HCl = ----------------- M
Amount of HCl = ---------------- grs/l
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3. Take 10 ml of given unknown HCl solution into 100 ml beaker and add 40 ml of
distilled water. The contents are shaken thoroughly.
4. The glass membrane electrode is dipped into the beaker containing the solution.
5. Initially at “0” Burette reading of NaOH solution, pH of the unknown HCl solution can
be measured.
6. Then 0.5 ml of base is added from the burette to the acid solution and on stirring
thoroughly the pH of the resultant solution can be noted.
7. The pH is noted every time by the addition of 0.5 ml base and finally you observe the
pH jump is between V1 and V2 ml. After pH jump you need to note about 10 readings.
8. Plot the graph with the volume of base on X - axis versus pH on Y-axis. Identify the
suitable jump which changes the medium from acidic pH to Basic pH.
9. Take the average in-between the jump values and draw a line which intercepts X axis.
The intersection point gives value of the equivalence point (End point) of acid and base
Report: S.No Given Amount of
unknown Acid Reported Amount of
unknown Acid % Error Marks Signature of the
Faculty 1
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Step-1: Observations & Calculations:
Burette : NaOH Solution
Conical Flask : 20 ml Oxalic Acid
Indicator : Phenolphthalein
End Point : Colour less to Pale pink.
S.No. Volume of Oxalic acid (v1 ml)
Burette readings (ml) Volume of NaOH Rundown (v2 ml) Initial Final
1
2
3
4
Calculations:
Oxalic Acid:
M1 = Molarity of Oxalic Acid = 0.05M
V1 = Volume of Oxalic Acid = 20 ml
n1 = Moles of Oxalic Acid = 1 mole
Sodium Hydroxide:
M2 = Molarity of NaOH =?
V2 = Volume of NaOH =
n2 = Moles of NaOH = 2 mole
Molarity of NaOH = -------------------------
= ------------------------
= ----------------- M
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EXPERIMENT-4
CONDUCTOMETRIC ESTIMATION OF ACID BY BASE
Aim: To determine the amount of unknown acid solution with standard base solution by
conductometric method.
Apparatus: Conductivity meter (with cell), burette (10ml), volumetric flask (100 ml),
beakers (100 ml), stirrer / glass rod.
Chemicals: Stock acid solution, 0.05 M oxalic acid in100ml volumetric flask and Stock base
solition.
PRINCIPLE: Conductometric titrations works on the principle of Ohm's law. As current is
inversely proportional to Resistance (R) and the reciprocal of resistance is termed as
Conductance, and its unit is Siemen (mho) cm-1. The electrical conductivity of a solution
depends on the number of ions and their mobility. In Conductometric titrations, the titrant is
added from the burette, and the conductivity readings are plotted against the volume of the
titrant. Upon adding a strong base to the strong acids, the conductance falls until the strong
acid is neutralized then raised. Such a titration curve consists of 2 lines which intersect at a
particular point, known as the End point or Equivalence point. The method can be used for
titrating coloured solutions or homogeneous, which cannot be used with normal indicators.
Strong Acid with a Strong Base:
For example, in the titration of HCl versus NaOH, the addition of a strong base
(NaOH) to a strong acid (Hcl). Before NaOH is added, the conductance is high due to the
presence of highly mobile hydrogen ions. When the base is added, the conductance falls due
to the replacement of hydrogen ions by the added cation as H+ ions react with OH- ions to
form undissociated water. This decrease in the conductance continues till the equivalence
point. At the equivalence point, the solution contains only NaCl. After the equivalence point,
the conductance increases due to the large conductivity of OH- ions.
H2C2O4 + 2 NaOH Na2C2O4 + 2H2O HCl + NaOH NaCl + H2O
Formula:
Procedure:
Step 1: Standardization of sodium hydroxide by using oxalic acid
1. Rinse and fill the burette with the given NaOH solution
2. Pipette out 20 ml of 0.05 M oxalic acid solution into a clean conical flask
3. Add 1 or 2 drops of phenolphthalein indicator to oxalic acid solution.
4. Titrate the solution against sodium hydroxide solution drop wise with shaking till the
solution changes to pale pin
5. Note the volume of NaOH used. It is the end point.
6. Repeat the titration until the concordant readings are obtained
7. Calculate the molarity of NaOH by using the formula mentioned above
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Observations and Calculations: Conductometric titration in between HCl and NaOH
Volume of base added
Conductance (C)
Corrected conductance
C1= C[(v+V)/V]
Volume of base added
Conductance (C)
Corrected conductance
C1= C[(v+V)/V]
0 8.0
0.5 8.5
1.0 9.0
1.5 9.5
2.0 10.0
2.5 10.5
3.5 11.0
4.0 11.5
4.5 12.0
5.0 12.5 5.5 13.0 6.0 13.5 6.5 14.0 7.0 14.5 7.5 15.0
v= Volume of NaoH, V= Total volume(50ml)
Calculation of Unknown molarity of HCl solution:
Sodium Hydroxide:
M2 = Molarity of NaOH =
V2 = Volume of NaOH =
n2 = Moles of NaOH = 1 mole
HCl:
M3= Molarity of HCl =?
V3= Volume of HCl = 25 ml
n3 = Moles of HCl = 1 mole
Molarity of HCl = ----------------- M
= ----------------------- M
Amount of HCl = ---------------- grs/l
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Step 2: Determination of molarity of unknown HCl by using standard NaOH through
conductometric titration
1. In 100 ml beaker take 25ml of given unknown HCl solution and add 25ml of distilled
water. The contents are shaken thoroughly.
2. Now, the conductivity cell is immersed in the beaker and the initial conductance of
the solution is taken by stirring the solution and keeping it constant.
3. Then, 0.5 ml portions of base is added from the burette and stirred well. The
conductance of the solution for each addition is to be noted.
4. The conductivity is corrected by multiplying with the factor [(v+V)/V], where 'v' is
the volume of base added and 'V' is the volume of solution initially taken in the beake
5. Plot the graph with respect to the volume of base consumed versus corrected
conductance. From the intersection point on the graph which gives value represents
the equivalence points of acid and base. Report: S.No Given Amount of
unknown Acid Reported Amount of
unknown Acid % Error Marks Signature of the
Faculty 1
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Observations & Calculations: Step-1: Standardization of EDTA Burette : EDTA Solution Concial Flask : 20 ml CaCl2 + 1 ml. of Ammonia Buffer Indicator : Erichrome Black-T Indicator End Point : Wine red to Sky Blue.
S.No. Volume of CaCl2 (v1 ml)
Burette readings (ml) Volume of EDTA Rundown (v2 ml) Initial Final
1 2 3 4
N1V1 = N2V2
Normality of calcium chloride (N1) = 0.02N
Volume of calcium chloride (V=) = 20 ml
Normality of EDTA (N2) = ?
Volume of EDTA (V2) = volume of EDTA rundown in ml
N2 = N1V1/V2
= ------------------ = -----------------
N2=---------------- N
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EXPERIMENT NO- 5
DETERMINATION OF TOTAL HARDNESS BY EDTA METHOD Sample Details:
Area: The water sample was collected from ______________
Source:
Aim: To estimate the total hardness present in the given water sample.
Apparatus: Burette, Burette Stand, Pipette, Conical Flask, Beaker, Wash Bottle, Glazed tile,
Glass Funnel.
Reagents: EDTA, CaCl2 (0.02N), Ammonia Buffer (pH=10), Erichrome Black-T (EBT)
indicator, Distilled Water.
Principle: In alkaline condition, EDTA reacts with Calcium and Magnesium to form
chelated complex. Ca and Mg develop winered colour with EBT indicator under alkaline
condition. When EDTA is added as titrant, Ca & Mg divalent ions get complexed resulting
in a sharp change from wine red to sky blue colour which indicates end point of the titration.
The pH for the titration has to be maintained at 10.0
complexEBTMg
CaEBT
Mg
Ca pH
10
2
2
Wine red (unstable)
EBTcomplexEDTAMg
CaEDTAcomplexEBT
Mg
Ca pH
10
Wine red (unstable) Stable Sky Blue Procedure:
Step-1: Standardization of EDTA
1) Take 20ml. CaCl2 (0.02N) solution in a clean conical flask.
2) To this add 1 ml. of Ammonia Buffer.
3) Add a pinch / 1 (or) 2 drops of EBT indicator.
4) The solution turns to Wine red colour.
5) Titrate with EDTA till the colour changes from Wine red to sky Blue.
6) Note down the volume of EDTA rundown (v2 ml).
7) Repeat the procedure till the concordant readings are obtained.
Step-2: Determination Total Hardness of water sample
1) Take 20ml. water sample in a clean conical flask.
2) To this add 1 ml. of Ammonia Buffer.
3) Add a pinch / 1 (or) 2 drops of EBT indicator.
4) The solution turns to Wine red colour.
5) Titrate with Std. EDTA till the colour changes from Wine red to sky Blue.
6) Note down the volume of EDTA rundown (v3 ml).
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Step-2: Determination Total Hardness of water sample Burette : Std. EDTA Solution Concial Flask : 20 ml water sample + 1 ml. of Ammonia Buffer Indicator : Erichrome Black-T Indicator End Point : Wine red to Sky Blue.
S.No. Volume of Water sample (ml)
Burette readings (ml) Volume of EDTA Rundown (v3 ml) Initial Final
1 2 3 4
Calculation of Total Hardness:
= V3 x N2 × 50 ×1000 ________________ Volume of Sample = _____________ = _________________ mg / litre
Total Hardness is = _______________ mg / litre or ppm
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Result:
Source of water sample Hardness (mg/l or ppm) Marks awarded Signature of the faculty
Significance:
1. The permissible limit of total hardness is 200 mg / litre as per W.H.O.
2. Absolutely softwater is tasteless and corrosion in nature.
3. Hardwater causes excessive consumption of soap.
4. Scales are formed in the boilers and reduce the heat efficiency of the boilers.
5. Important in determining the suitability of water for domestic and industrial use.
6. Determination of hardness serves as a basis for routine control of softening process
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CYCLE-2 EXPERIMENTS
Expt.
No.
Experiment CO Page
No.
6 Colorimetric Determination Of Iron (III). CO5 30
7 Potentiometric Determination Of Mohr’s Salt Using
K2Cr2O7.
CO2 34
8
a Estimation Of Viscosity Of An Organic Solvent By Using
Ostwald Viscometer.
CO2 38
b Determination of Surface Tension of Given Liquid by
Stalagmometer
40
9 Determination of Chloride content present in given water
sample.
CO3 42
10
a Determination of Kinematic Viscosity Of a Given Oil
Sample By Using Viscometer.
CO1 46
b Preparation of Bakelite (Phenol-Formaldehyde Resin) Polymer
CO4 50
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Known Iron(III):
S.NO Volume of Iron(III) sample in ml
Absorbance / Optical density
1 5
2 10
3 15
4 20
5 25
6 30
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EXPERIMENT – 6 Date: COLORIMETRIC ESTIMATION OF IRON (III) WITH THIOCYANATE
Aim: To estimate ferric ion using thiocyanate as complexing agent.
Reagents:
1. Ferric ion solution: In a 250 ml volumetric flask 0.432 gm of Ammonium ferric
sulphate is weight. To this 5 ml conc. HCl is add to produce clear solution. The solution
make up to 250 ml with distilled water.
2. 10% Potassium thiocyanate (KSCN): 10 gm of KSCN crystals are dissolving in 100
ml of distilled water.
3. 4N Hydrochloric acid: 18.5 ml of conc. HCl is dilute to 100 ml with distilled water.
4. Working solution: 5 ml of ferric ion solution is dilute to 250 ml in a volumetric flask
with distilled water.
Theory: Ferric ion reacts with thiocyanate to give a series of intensified red color
compounds. These complexes are red and can be formulated as [Fe(SCN)n]2+ where n = 1,2-
---6. At low thiocyanate concentration the predominant colour complex is [Fe(SCN)]2+. At
very high SCN- concentration, it is [Fe(SCN)6]3-
Fe3+ + SCN- [Fe(SCN)]2+
Principle:
Iron is one of the many minerals required by the human body. It is used in the
manufacture of the oxygen-carrying proteins, haemoglobin and myoglobin. A deficiency of
iron in the body can leave a person feeling tired and listless, and can lead to a disorder called
anemia. Many of the foods we eat contain small quantities of iron. In this analysis the iron
present in an iron tablet (dietary supplement) or a sample of food is extracted to form a
solution containing Fe3+ (ferric) ions. To make the presence of these ions in solution visible,
thiocyanate ions (SCN−) are added. These react with the Fe3+ ions to form a blood-red
coloured complex.
By comparing the intensity of the colour of this solution with the colours of a series of
standard solutions, with known Fe3+ concentrations, the concentration of iron in the tablet or
food sample may be determined. This technique is called colorimetry.
Colorimeter measures the optical density of an absorbing substance where optical density
(O.D) is defined as O.D = log 1oI
I ; Where
oI = Intensity of incident light; I =
Intensity of transmitted light. As per beers law, optical density of an absorbing substance is related to the concentration by the equation. . . .O D E C l (or) . ( . ). 2O D E l C
Where ‘C’ is the concentration of the substance, l is the path length, which represents the width of the cell used and is constant for a given cell used, E is the molar absorption coefficient and is a constant for given substance. Equation 2 may be written as
O.D. C 3 Equation 3 represents the quantitative form of Beer’s law. If the optical density of a substance is determined at varying concentration, a plot of O.D. Vs C gives a straight line
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Unknown Iron(III):
S.NO Volume of Iron(III)
sample in ml Absorbance /
Optical density
1 Unknown-I
2 Unknown-II
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Procedure:
1. About six 50 ml volumetric flasks are take and into each flask x ml (i.e, x= 5 to 30)of
iron(III) ion solution, 5 ml of 10% thiocyanate solution and 4 ml of 4N HCL are run
down the solution is make up to the mark instantaneously well shake the solution.
2. Add same quantities of 10% thiocyanate solution and 4N HCL to unknown iron (III)
samples and make up to the mark instantaneously well shake the solutions.
3. The optical density (OD) of each sample is measure with 490 nm visible light
immediately. This cyanate complex is unstable, so the readings are taking quickly.
4. A graph is draw with OD along y-axis and volume of the iron (III) along x-axis for
known solutions. The graph is obtained is a straight line.
5. Using optical density values of unknown samples determine the volume of unknown
iron (III) from graph.
Report:
S.NO. Volume of Iron(III)
given (ml)
Volume of Iron(III)
reported (ml)
% Error Marks Signature of the
faculty
1
2
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KNOWN:
Pilot Titration Accurate Titration S.NO. Volume of K2Cr2O7 Potential in volts S.NO. Volume of K2Cr2O7 Potential in volts
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EXPERIMENT NO-7 Date:
Potentiometric titration of iron (II) Vs potassium dichromate Aim: To determine the concentration of Ferrous ammonium sulphate using standard
potassium dichromate following a potentiometric method.
Apparatus: Potentiometry, Standard calomel electrode,
Solutions required: 0.1N K2Cr2O7, 0.1N Ferrous ammonium sulphate and 1:1 H2SO4
General Principle:
Potentiometric Titrations: Potentiometric titrations involve the measurement of the
potential of a suitable indicator electrode with respect to a reference electrode as a function of
titrant volume. Potentiometric titrations provide more reliable data than data from titrations
that use chemical indicators and are particularly useful with colored or turbid solutions and
for detecting the presence of unsuspected species.
A typical cell for potentiometric analysis consists of a reference electrode, an indicator
electrode and a salt bridge. This cell can be represented as
A reference electrode, Eref, is a half-cell having a known potential that remains constant at
constant temperature and independent of the composition of the analyte solution. The
reference electrode is always treated as the left-hand electrode in potentiometric
measurements. Calomel electrodes and silver/silver chloride electrodes are types of reference
electrodes. An indicator electrode has a potential that varies with variations in the
concentration of an analyte. Most indicator electrodes used in potentiometry are selective in
their responses. Metallic indicator electrode and membrane electrodes are types of indicator
electrodes. The third component of a potentiometric cell is a salt bridge that prevents the
components of the analyte solution from mixing with that reference electrode. A potential
develops across the liquid junctions at each end of the salt bridge. The junction’s potential
across the salt bridge, Ej, is small enough to be neglected. The potential of the cell is given by
the equation;
Ecell= Eind – Eref + Ej
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UNKNOWN:
Pilot Titration Accurate Titration S.NO. Volume of K2Cr2O7 Potential in volts S.NO. Volume of K2Cr2O7 Potential in volts
Calculation:
Known: 20 ml of Fe(II) solution consume x ml of Cr(VI)
Unknown: x ml of Cr(VI) solution consume 20 ml of Fe(II) solution
y ml of Cr(VI) solution consume ? ml of Fe(II) solution
? ml = y×20/x
20 ml of Fe(II) solution contains = ? ml of Iron
100 ml of Fe(II) solution contains = ?? ml of Iron
?? = ?×100/20
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Procedure:
1. 20.00 ml of ferrous ammonium sulphate is transferred to a 100 ml beaker by means of
burette.
2. To this 15.00 ml of distilled water and 5.00 ml of 1:1 H2SO4 are added and the
contents are shaken thoroughly.
3. The platinum electrode placed in the beaker the being connected to the positive end of
the potentiometer.
4. After measuring the emf of the solution in the beaker, the standard K2Cr2O7 add from
the burette in one ml portion while stirring the content in the beaker with glass rod
and corresponding e.m.f are note down.
5. At a certain point a sudden raise in potential is observed this shows that the end point
is in between these additions where the jump is observed thus titrated readings are
called point readings by which are can get the end point approximately.
6. Again taking the same content in the beaker and titrated with standard K2Cr2O7 in the
same manner by the addition of 1 ml dichromate solution up to the jump reading. But
in between point readings add only 0.1 ml dichromate and note down potential
readings.
7. After the end point 4-5 ml of dichromate is added in ml portion and the corresponding
readings are note down.
8. The plot is made between the e.m.f values as ordinate (Y-axis) and volume of
dichromate added as the abscissa (X-axis). The volume of dichromate corresponding
to the point of inflection gives the equilibrium point for the titration.
9. The same procedure is repeat for the unknown solution of Fe(II). From their
equilibrium points the unknown volume is calculate from this its concentration can
also calculate.
Report:
S.NO. Volume of Fe(II) % Error Faculty
Signature Given Reported
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Observations & Calculations:
Water
Time of flow
Average time
Benzene / Aniline/ Toulene
Time of flow
Average time
Densities of different organic liquids:
Name of the Organic Liquid
Density in gr./cc
BENZENE 0.8737 TOULENE 0.8625 ANILINE 1.02
Calculations:
l
w
l
w
l
w
t
t.
?...................l
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EXPERIMENT – 8(a) Date: DETERMINING THE COEFFICIENT OF VISCOSITIES OF DIFFERENT LIQUIDS Aim: To determine the coefficient of viscosities of various liquids like benzene, Aniline and acetic acid. Principle: Resistance to flow of a liquid is known as viscosity. The retarding force is proportional to the area of contact and the velocity gradient. The proportionality constant ‘η’ is the coefficient of viscosity, and is characteristic of a liquid. When a liquid flows through a capillary tube, η = πρr4t/8Vl, where ‘ρ’ is the density of liquid, ‘r’ is the radius of the tube, ‘t’ is the time of flow, ‘l’ is the length of the capillary tube and V is the volume of liquid. This is called absolute viscosity determination. But if the same volumes of two liquids are allowed to flow through the same tube, then we have the relation.
l
w
l
w
l
w
t
t.
ηw =Viscosity of water; ηl = Viscosity of given organic liquid;
ρw= Density of water; ρl= Density of given organic liquid
tw= Time of flow of water; tl= Time of flow of given organic liquid
If the viscosity of one liquid is known, then the other can be calculated. An Ostwald’s viscometer is used to determine relative viscosity of liquids
Procedure: 1. An Ostwald viscometer is cleaned by rinsing three times with small volumes of acetone
and dried. 2. The lower bulb is filled with distilled water and clamped vertically. 3. A rubber bulb is attached to the tip of the narrow limb and the liquid drawn up to a level
much above the upper mark. 4. The rubber bulb is removed and the liquid allowed to flow down freely. 5. A stop watch is started just as the liquid meniscus passes the upper mark and stopped
when it passes the lower mark. 6. The time of flow ‘tw’ is noted. Density of water is 0.9971 gr./cc and ‘ηw’ for water is
8.94 milli poise at 250C. 7. The viscometer is again cleaned and dried as before. It is then filled with the experimental
liquid (Benzene, Toluene, Aniline and Glacial acetic acid). 8. Time of flow ‘tl’ is determined as in the case of water. The densities of the liquids may
either be determined or taken from literature. 9. The coefficient of viscosity ‘ηl’ of the liquid can be calculated.
Result: Name of the
Given Organic solvent
Coefficient of viscosity (m.p) Marks awarded
Signature of the faculty
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Weight of empty specific gravity bottle = w1gram
Weight of specific gravity bottle + water = w2 gram
Weight of empty specific gravity bottle + liquid = w3gram
Weight of water= (w2-w1) gram
Weight of liquid = (w3-w1) gram
Calculations:
Density of the water dl = (w2 –w1) / volume of water
Density of the liquid d2 = (w3 –w1) / volume of liquid
γ2 / γ1 = (d1/d2) × (n2/n1)
γ1 = Surface tension of water = 72 dyn/cm γ2 = Surface tension of liquid d1 = Density of water d2 = Density of liquid n1= Number of drops of water n2 = Number of drops of liquid
γ2 = (d1/d2) × (n2/n1) × γ1 dynes/cm
= -----------------
= -----------------
= ------------------ dynes/cm
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EXPERIMENT - 8(b) Date:
Determination of Surface Tension of Given Liquid by Stalagmometer
Aim: Determine the surface tension of a given liquid at room temp using stalgmometer by
drop number method
Requirements: Stalgmometer, specific gravity bottle, a small rubber tube with a screw pinch
cork, distilled water, experimental liquid.
Theory: In the drop number method, the number of drops formed by equal volumes of two
liquid is counted. If m1, m2 are the mass of the liquid having densities d1 and d2 respectively.
If n1 and n2 is the number of drops formed by volume v of the two liquids, then their surface
tensions are related as
γ2 / γ1 = (d1/d2) × (n2/n1)
Procedure:
1. Clean the stalgmometer with chromic acid mix, wash with water and dry it.
2. Attach a small piece of rubber tube having a screw pinch cock at the upper end of the
stalgmometer.
3. Immerse the lower end of the stalgmometer in distilled water and suck the water 1-2cm
above mark A. adjust the pinch cork so that 10-15 drops fall per minute.
4. Clamp the stalgmometer allow the water drops to fall and start counting the number of
drops when the meniscus crosses the upper mark A and stop counting when the meniscus
passes mark B.
5. Repeat the exercise to take three to four readings.
6. Rinse the stalgmometer with alcohol and dry it.
7. Suck the given liquid in the stalgmometer and count the drops as in case of water.
8. Take a clean dry weighing bottle weighs it with water as well as with liquid.
Result:
The surface tension of liquid is ……… dynes/cm
Name of the liquid surface tension of liquid in dynes/cm
Marks awarded Signature of the faculty
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Experiment: 9 Date: DETERMINATION OF CHLORIDE CONTENT PRESENT IN WATER SAMPLE
Aim: To determines the chloride content present in given water sample.
Apparatus: Burette, Measuring cylinder, Beaker, Dropper, Stirrer,
Reagents: Potassium chromate indicator, Silver nitrate solution (0.0141 N)
Introduction: Chlorides occur in all natural waters in widely varying concentration, the chloride content normally increases as the mineral content increases. Upland and mountain supplies usually are quite low in chlorides, whereas river and groundwater usually have a considerable amount. Sea and ocean waters represent the residues resulting from partial evaporation of natural waters that flow into them and chloride levels are very high. Chlorides gain access to natural waters in many ways. The solvent power of water dissolves chlorides from topsoil and deeper formations. Spray from the ocean is carried inland as droplets or as minute salt crystals, which result from evaporation of the water in the droplets. These sources constantly replenish the chlorides in inland areas where they fall. Groundwater in areas adjacent to the ocean is in hydrostatic balance with seawater. Human excreta, particularly urine, contain chloride in an amount about equal to the chlorides consumed with food and water. This amount average about 6 gm of chlorides per person per day and increases the amount of CC in municipal wastewater about 15 mg/l above that of the carriage water. Thus, wastewater effluents add considerable chlorides to receiving streams. Many industrial wastes (e.g., tannery waste) also contain appreciable amount of chlorides. Environmental significance: Chlorides in reasonable concentrations are not harmful to human. At concentrations above
250 mg/L they give a salty taste to water, which is objectionable to many people. For this
reason, chlorides are generally limited to 250 mg/L in supplies intended for public use.
Principle: (Mohr’s Method) This method determines the chloride ion concentration of a solution by titration with silver nitrate. As the silver nitrate solution is slowly added, a precipitate of silver chloride forms.
Ag+(aq) + Cl–(aq) → AgCl(s) The end point of the titration occurs when all the chloride ions are precipitated. Then additional silver ions react with the chromate ions of the indicator, potassium chromate, to form a red-brown precipitate of silver chromate.
2Ag+(aq) + CrO42–(aq)→ Ag2CrO4(s) (reddish brown precipitate)
This method can be used to determine the chloride ion concentration of water samples from
many sources such as seawater, stream water, river water and estuary water. The pH of the
sample solutions should be between 6.5 and 10. If the solutions are acidic, the gravimetric
method or Volhard’s method should be used.
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Observation:
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Procedure:
1. Take 50 mL of the sample in a beaker and add 5 drops (about 1 mL) of potassium
chromate indicator to it.
2. Add standard (0.0141 N) silver nitrate solution to the sample from a burette, a few
drops at a time, with constant stirring until the first permanent reddish color appears.
Record the mL of silver nitrate used.
Result:
Sample and Source of water
Chloride (mg/l or ppm) Marks awarded Signature of the faculty
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Observation and Calculations:
S. No. Temperature Time required to
flow 50 ml of oil (in Seconds)
Kinematic Viscosity
(Centistokes) V = At – B/t
Average Kinematic Viscosity
(Centistokes)
The kinematic viscosity of the liquid is given by the formula
V = At - B/t
V = Kinematic viscosity of oil in centistokes
t = Time of flow for 50 ml of oil in seconds
A and B are instrument constants
S. No Type of
equipment Time of flow A value B value
1 Redwood 1 40 to 85 secs 0.264 190 2 Redwood 1 85 to 2000 secs 0.247 65 3 Redwood 2 --- 0.027 20
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EXPERIMENT – 10(a) Date:
ESTIMATION OF KINEMATIC VISCOSITY OF THE GIVEN LUBRICATING OIL
Aim: To determine the kinematic viscosity of given lubricating oil at a given temperature by using Redwood Viscometer
Principle: The internal drag arises between two successive layers of the liquid is known as viscosity. Further, the force per unit area required to maintain the velocity gradient by one unit between two successive layers of one unit length apart is known as viscosity coefficient. High viscous liquids move slowly while low viscous liquids move fast through a given capillary. Further, the time required to flow a given volume of liquid through a capillary depends on its viscosity. Therefore, the viscosity of liquid can be determined by determining the time required to flow the known volume of liquid through a standard capillary. Viscosity is expressed in poise.
Procedure:
The Redwood viscometer consists of oil cup which is opened at the upper end and it is fitted with an orifice
It is cleaned thoroughly with suitable solvent and then dried The orifice is covered with brass ball to stop the flow of oil The oil cup is placed in the cylindrical copper vessel which serves as water bath The bath is filled with suitable liquid which has the boiling point higher than the
temperature at which the viscosity of oil to be determined If the viscosity of the oil is to be determined at 800C or below, the bath is filled with
water The instrument level is adjusted on the tripod stand with the help of the leveling screws Now the oil cup is filled with oil to be tested carefully up to the level indicated and the
covered with lid Two thermometers, one is in the oil and the other one is in the liquid (water) are
immersed Similarly two stirrers also placed in the oil and the liquid One 50 ml flask is kept in position below the jet Now the oil is heated slowly with constant stirring of oil and the water until it reaches to
the required temperature at which the viscosity of the oil is to be determined When the temperature of the oil has quite steady and reaches the required temperature,
the brass ball is lifted and simultaneously the stop watch is started. The oil is allowed to flow through the orifice and collected in the flask Stop watch is stopped when 50 ml of oil is collected in the flask up to the mark and
immediately the orifice is covered with brass ball to stop the over flow of the oil The time required to flow the 50 ml of oil is noted The oil cup is refilled again with oil and same procedure is repeated for five to six times The viscosity of oil is calculated at given temperature
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Precautions The oil should be filtered through a 100 mesh wire sieve before testing for its
viscosity Receiving flask should be placed in such a way that the oil jet touches inside layer of
the flask and does not form foaming Same receiving flask should be used for all readings After each reading, oil should be completely drained out of the receiving flask and it
should be thoroughly cleaned and dried Report:
Name of the Lubricating Oil
Average of kinematic viscosity
(Centistokes)
Marks awarded
Signature of the faculty
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Step-1: formation of o,p methyl phenol:
Step-2; formation of novalac:
Step-3: formation of bakelite:
1: formation of o,p methyl phenol:
2; formation of novalac:
3: formation of bakelite:
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Experiment – 10 (b) Date: PREPARATION OF PHENOL-FORMALDEHYDE RESIN (BAKELITE)
Aim: To prepare the phenol – formaldehyde resin
Principle:
Phenol formaldehyde resins (PF) include synthetic thermosetting resins such as bakelite obtained by the reaction of phenols with formaldehyde. Phenol-formaldehyde resins are formed by a step-growth polymerization reaction that can be either acid- or base-catalysed.
Phenol is reactive towards formaldehyde at the ortho and para sites (sites 2, 4 and 6) allowing up to 3 units of formaldehyde to attach to the ring. The initial reaction in all cases involves the formation of ortho & para hydroxymethyl phenols. The ortho hydroxymethyl phenol undergoes linear polymerization to form novalac which is fusible and soluble in most of the organic solvents. Novolacs are phenol-formaldehyde resins made where the molar ratio of formaldehyde to phenol of less than one. Hexamethylene tetramine or "hexamine" is a hardener that is added to crosslink novolac. At ≥180 °C, the hexamine forms crosslink’s to form methylene and dimethylene amino bridges. Base-catalysed phenol-formaldehyde resins are made with a formaldehyde to phenol ratio of greater than one (usually around 1.5). These resins are called resols.
When the molar ratio of formaldehyde: phenol reaches one, every phenol is linked together via methylene bridges, generating one single molecule, and the system is entirely crosslinked. In bakelite, this ratio is greater than one, and so it is very hard
Procedure:
5.0 ml of phenol is weighed and transferred into a clean and dried 250 ml beaker. 7 ml of formaldehyde solution is added carefully. (Caution : Avoid the inhaling the
vapours and spilling of it on body) 5.0 ml of glacial acetic acid and one or two spatula of hexamine (hexamethylene
tetramine) are added The contents of the beaker are heated gently in a water bath. The beakers is removed from the water bath and add conc. hydrochloric acid slowly
drop-wise with constant stirring. After the addition of hydrochloric acid a white substance precipitates first. Finally, a
pink colored plastic clump is formed at the bottom of the beaker while stirring. The plastic clump is now washed with distilled water for several times and then dried
in a oven Now the sample is weighed and its weight is reported
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Precautions:
Formaldehyde solution 37 % is very toxic by inhalation, ingestion and through skin absorption. Readily absorbed through skin. Probable human carcinogen. Mutagen. May cause damage to kidneys, allergic reactions, sensitization and heritable genetic damage.
Phenol is acute poisoning by ingestion, inhalation or skin contact may lead to death. Phenol is readily absorbed through the skin. Highly toxic by inhalation.
Safety glasses and protective gloves required. The experiment should be performed under a portable fume cupboard giving all-round visibility
Report:
Amount of Resin formed
Marks awarded Sign. of the faculty
