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Laboratory Manual
ENGINEERING CHEMISTRY LAB MANUAL
CODE NO : CYUBLB
(B.Tech Ist^ Semester)
Course Instructor: Dr. Sunil Kumar Singh
गु� घासीदास िव�िव�ालय, िबलासपुर, (छ.ग.) Guru Ghasidas Vishwavidyalaya, Bilaspur A Central University established by the Central University Act 2009 No. 25 of 2009
01. (^) Standardization of sodium thiosulfate solution by standard potassium **dichromate solution. 9-
- To**^ determine^ the^ Normality^ and^ Strength^ (g/L)^ of^ given^ Ferrous Ammonium Sulfate solution‘A’ using standard Ferrous Ammonium Sulfate (N/30) solution ‘B’ taking KMnO 4 solution as an intermediate.
03. To^ determine the concentration of hypo solution (Na 2 S^2 O 3 .5H 2 O) iodometrically with given Iodine (N/50) solution. (^16) 04. Find out the Temporary hardness of given water sample using 0.01M EDTA solution, buffer solution (pH-10) and EBT as an indicator. (^) **17-
- To determine chloride ion in a given water sample by Argentometric method** (Mohr’s method). (^) 20-
01. To calculate the λmax of a given compound using UV-visible
spectrophotometer. 30-
02. To separate the metallic ions by paper chromatography. 32-
Contents
01. Chemistry laboratory safety precautions. 4-
02. Laboratory Equipment 6-
03. Experimental Section
Section-A
Section-B
Section-C
01. Preparation of Urea Formaldehyde resin. 22-
02. Acetylation of Primary Amine: Preparation of Acetanilide. 24
03. Base Catalyzed Aldol Condensation: Synthesis of dibenzalpropanone. 25-
04. [4+2] Cycloaddition Reaction: Diels-Alder reaction. 27
05. Preparation of aspirin and calculate its yield. 28-
SECTION-A
SECTION-B
SECTION-C
GENERAL CHEMISTRY LABORATORY RULES
Never eat or drink in the lab. Food may pick up toxic chemicals.
Keep the apparatus scrupulously clean.
Keep the reagents in their proper places after use. Do not alter their position.
Do not contaminate the reagents.
Never taste any chemical. Some chemicals are very corrosive and poisonous in very small quantities.
Keep gas taps and water taps closed when not in use.
Use either spirit lamp or candle to light the burner.
Never put anything back into a reagent bottle. Once a reagent has passed the mouth of its container, it has passed the point of no return.
Always take as little of a chemical as possible. Use only clean, dry spatulas for removing chemicals from bottles. Properly dispose of excess chemicals.
Do not throw any waste paper /litmus paper etc. into the sink. Throw them into the dust bin.
Rinse spills off skin immediately. Rinse off any chemicals spilled on the skin immediately with large amounts of water.
Do not pour concentrated acids into the sink. If they are to be poured, flush them with water.
To be a better analyst, understand the theory of the experiments you conduct.
Record your observations as and when you proceed (and not after completion) in a note book and keep it away from reagents and sink.
Properly dispose of waste chemicals. Certain liquids can be poured into the sink and flushed with water while others are poured into designated waste containers. Most solid wastes are placed in designated crocks. Your instructor will provide disposal instructions each lab.
Wear a Lab Coat and Safety Goggles and also have a Lab Manual and Calculator while performing experiments in the laboratory. Without them, you are not allowed to enter the lab section.
Eating, Drinking, Smoking, and Cellphones are Forbidden in the laboratory at all times. Avoid unnecessary movement and talk in the laboratory.
Any accident involving even the most minor injury must be reported to the lab assistants.
Do not attempt any unauthorized experiment. Perform only lab operations and activities
BURETTE : Burette is a vertical cylindrical piece of laboratory glassware with a volumetricgraduation on its full length and a stopcock on the bottom. It is used to dispenseknown amounts of a liquid reagent in a titration experiment.
STAND : A metal rod attached to a heavy metal base. The
heavy base keeps the stand stable, and the vertical metal rod
allows for easy height adjustment of the ironring/clamp.
FUNNEL : Funnels are used for pouring liquids from one container to another. In addition, with the aid of filter paper, they can be used as separation devices to separate liquids fromsolids. It is fixed by a ring support on a stand.
Filter paper : paper is used to separate solid particles
from liquids. They can have differentsize with different pore
size.Solids that remain on filter paper can later be dried on a
watch glass or in an oven.
WATCH GLASS : Watch glass is used to allowcrystal
to dry after they have been filtered. They canbe used as an
evaporating surface or to cover a beaker that can be heated to
very high temperatures.
STALAGNOMETER : A stalagmometer is a glass instrument that measures the surface tension of a liquid.
VISCOMETER : Instrument for measuring the viscosity (resistance to internal flow) of a fluid.
5. Appearance of milky colour indicate end point. Note the volume of sodium thiosulfate used till
end point.
6. Repeat the process thrice for better results.
7. Take difference of volume of sodium thiosulfate used in procedure of potassium dichromate
and blank experiment and use that volume in calculations.
Calculations:
Volume of K 2 Cr2 O 7 used = 10ml Sr no.
Burette reading (Initial)(ml)
Burette reading (Final) (ml)
Final Volume (ml)
1.
2. 3.
Volume of Na 2 S 2 O 3 used for burette according to experimental values = Vs = ml
Blank Experiment:
Sr no.
Burette reading (Initial)(ml)
Burette reading (Final) (ml)
Final Volume (ml)
**1.
3.**
Average volume of Na 2 S 2 O 3 used during blank experiment = Vy = ml Volume of Na 2 S 2 O 3 used =VS - V (^) Y = ml Volume of K 2 Cr2 O 7 = V 1 = 10 ml Normality of K 2 Cr2 O 7 = N 1 = Normality of Na 2 S 2 O 3 = N 2 =?
K 2 Cr 2 O 7 : Na 2 S 2 O 3 N 1 V 1 = N 2 V 2
Results: The strength of Na 2 S 2 O 3 solution is = g/L
Precautions :
- Keep your eye in level with the liquid surface while taking the burette reading or while reading the pipette or measuring flask etc.
- Always read lower meniscus in case of colourless solution and upper meniscus in case of coloured solutions.
- Do not blow through the pipette to expel the last drop of solution from it, simply touch the inner surface of the titration flask with the nozzle of the pipette for this purpose.
To determine the Normality and Strength (g/L) of given Ferrous Ammonium Sulfate
solution ‘A’ using standard Ferrous Ammonium Sulfate (N/30) solution ‘B’ taking
KMnO4 solution as an intermediate.
Theory: Potassium permanganate is a strong oxidant in the presence of sulfuric acid. Mohr salt is a
double salt forming a single crystalline structure having the formula FeSO 4 .(NH 4 ) 2 SO 4 .6H 2 O. The
chemical name for Mohr’s salt is ferrous ammonium sulfate.
In this titration Mohr salt acts as a reducing agent and potassium permanganate acts as an oxidizing
agent. So, the reaction between Mohr’s salt and potassium permanganate is a redox reaction. In this
redox reaction, ferrous ion from Mohr’s salt gets oxidized and pink colored of manganese present in
potassium permanganate, which is in the +7 oxidation state gets reduced to colorless Mn2+^ state.
The chemical reaction and the molecular chemical equation is given below.
Reduction half reaction –
2KMnO 4 + 3H 2 SO 4 → K 2 SO 4 + 2MnSO 4 + 3H 2 O + 5[O]
Oxidation half reaction –
[2FeSO 4 (NH 4 )2SO 4 .6H 2 O + H 2 SO 4 + [O] → Fe 2 (SO 4 ) 3 + 2(NH 4 )2SO 4 + 13H 2 O] x 5
Overall reaction –
2KMnO 4 + 10FeSO 4 (NH 4 )2SO 4 .6H 2 O+ 8H 2 SO 4 → K 2 SO 4 + 2MnSO 4 + 5Fe 2 (SO 4 ) 3 + 10(NH 4 )2SO 4 +
68H 2 O
The ionic equation involved in the process is given below.
Oxidation half reaction – [Fe2+^ → Fe3+^ + e–^ ] x 5
Reduction half reaction – MnO4–^ + 8H+^ + 5e– → Mn2+^ + 4H 2 O
Overall ionic equation – MnO4–^ + 8H+^ + 5Fe2+^ → Mn2+^ + 5Fe3+^ + 4H 2 O
This titration is based upon oxidation-reduction titrations. When ferrous ammonium sulfate solution is
titrated against potassium permanganate in the presence of acidic medium by sulfuric acid. Acidic
medium is necessary in order to prevent precipitation of manganese oxide. Here KMnO 4 acts as a self
indicator and this titration is called permanganate titration.
Materials Required:
1. Mohr’s salt (ferrous ammonium sulfate) 2. Potassium permanganate solution
12. Record the reading in the observation table given below in order to calculate the molarity of
KMnO 4 given.
C. Titration of potassium permanganate solution against given ferrous ammonium sulfate (Mohr’s salt) solution:
- Wash and rinse the burette and pipette with distilled water and then rinse with the corresponding solution to be filled in them.
- Rinse the burette with the potassium permanganate solution and fill the burette with potassium permanganate solution.
- Fix the burette in the burette stand and place the white tile below the burette in order to find the endpoint correctly.
- Rinse the pipette and conical flask with given ferrous sulfate solution.
- Pipette out 10ml of given standard Mohr’s salt solution into the conical flask.
- Add a test tube full of sulfuric acid in order to prevent oxidation of manganese to form manganese dioxide.
- Note down the initial reading in the burette before starting the titration.
- Now start the titration, titrate against potassium permanganate solution and simultaneously swirl the solution in the flask gently.
- Initially, the purple colour of KMnO 4 is discharged with ferrous ammonium sulfate. The appearance of a permanent pink colour reveals the end point.
- Repeat the titration until concordant values are obtained.
- Note down the upper meniscus on the burette readings.
- Record the reading in the observation table given below in order to calculate the normality of given.
Observations: Titration of potassium permanganate solution against N/30 standard ferrous
ammonium sulfate (Mohr’s salt) solution:
S.No Volume of ferrous ammonium sulfate (Mohr’s salt) used
Burette Reading Volume(V) of KMnO 4 used V = (y-x)ml
Initial(x) Final(y)
Observations: Titration of potassium permanganate solution against given ferrous ammonium sulfate
(Mohr’s salt) solution:
S.No Volume of ferrous ammonium sulfate (Mohr’s salt) used (given)
Burette Reading Volume(V) of KMnO4 used V = (y-x)ml
Initial(x) Final(y)
Calculations:
(a) Normality of KMnO 4 solution:
Consider y ml of given KMnO 4 solution is equivalent to 20ml of N/10 Mohr’s salt solution.
According to law of equivalents,
N 1 V 1 = N 2 V 2
- N 1 , N 2 are normality of Mohr’s salt and KMnO 4 solution respectively.
- V 1 , V 2 are volumes of Mohr’s salt and KMnO 4 respectively.
1/10 x 20 = N 2 x y
N 2 = 2/y
N = Normality of given KMnO 4 solution = 2/y
(b) Normality of given Ferrous ammonium sulfate solution:
NV = N 3 V 3
- N 3 , N are normality of given Mohr’s salt and KMnO 4 solution respectively.
- V 3 , V are volumes of given Mohr’s salt and KMnO 4 respectively.
N 3 = V 3 /NV
To determine the concentration of hypo solution (Na 2 S 2 O 3 .5H 2 O) iodometrically
with given Iodine (N/50) solution.
Theory : Iodine reacts with sodium thiosulfate as follows :
I 2
2I- + S 4 O 6 2-
Chemical required :
1. Given sodium thiosulfate solution
2. Iodine solution
3. Distilled water
4. Starch solution (10%)
Procedure :
- Rinse and fill the burette with the given sodium thiosulfate solution.
- Pipette out 20ml of the provided Iodine solution into a conical flask.
- To it add 20ml of water.
- Keep the flask below the nozzle of the burette.
- Now run down sodium thiosulfate solution from the burette into the conical flask till a light yellow colour is obtained.
- Now add 2-3ml of starch solution.
- A deep blue colour is obtained.
- Again, add sodium thiosulfate solution drop by drop till the blue colour just disappears.
- Repeat the titration till concordant values are obtained.
Calculation : Suppose 20ml of Iodine solution = V ml of Hypo solution 20 x N/50 = V x N (^) Na2S2O Or N (^) Na2S2O3 = 2N/5V
Result : The Normality and strength of given hypo solution is ………
Precautions:
1. Keep your eye in level with the liquid surface while taking the burette reading or while reading
the pipette or measuring flask etc.
2. Always read lower meniscus in case of colourless solution and upper meniscus in case of
coloured solutions.
3. Do not blow through the pipette to expel the last drop of solution from it, simply touch the inner
surface of the titration flask with the nozzle of the pipette for this purpose.
Find out the Temporary hardness of given water sample using 0.01M EDTA solution,
buffer solution (pH-10) and EBT as an indicator.
Principle:
Hardness in water is due to the presence of dissolved salts of calcium and magnesium. It is unfit
for drinking, bathing, washing and it also forms scales in boilers. Hence it is necessary to
estimate the amount of hardness producing substances present in the water sample. Once it is
estimated, the amount of chemicals required for the treatment of water can be calculated.
The estimation of hardness is based on complexometric titration. Hardness of water is
determined by titrating with a standard solution of ethylene diamine tetra acetic acid (EDTA)
which is a complexing agent. Since EDTA is insoluble in water, the disodium salt of EDTA is
taken for this experiment. EDTA can form four or six coordination bonds with a metal ion.
1. Total hardness
Total hardness is due to the presence of bicarbonates, chlorides and
sulphates of calcium and magnesium ions. The total hardness of water is estimated by titrating
the water sample against EDTA using Eriochrome Black-T (EBT) indicator. Initially EBT
forms a weak EBT-Ca2+/Mg2+ wine red coloured complex with Ca2+/Mg2+ ions present in
the hard water. On addition of EDTA solution, Ca2+/Mg2+ ions preferably forms a stable
EDTA-Ca2+/Mg2+ complex with EDTA leaving the free EBT indicator in solution which is
steel blue in colour in the presence of ammonia buffer (mixture of ammonium
chloride and ammonium hydroxide, pH 10).
2. Temporary hardness
Temporary hardness is due to the presence of bicarbonates of calcium and magnesium ions. It
can be easily removed by boiling. When water is boiled, temporary hardness producing
substances (bicarbonates) are precipitated as insoluble carbonates or hydroxides. This
precipitate can be removed by filtration. (The filtrate is used in the next step).
3. Permanent hardness
Permanent hardness is due to the presence of chlorides and sulphates of calcium and
magnesium ions. This type of hardness cannot be removed by boiling. The filtrate obtained
from the above step contains permanent hardness producing substances and is estimated against
EDTA using EBT indicator.
Chemicals Required :
1. Distilled water
2. EDTA solution
3. EBT
4. Buffer solution
Procedure:
The burette is filled with standard EDTA solution to the zero level, following
usual precautions.
1. Estimation of Total Hardness
20 ml of the given water sample is pipetted out into a clean conical flask. 5 ml
ammonia buffer and 2 drops of EBT indicator are added and titrated against EDTA
from the burette. The end point is the change of colour from wine red to steel blue.
Volume of hard water taken =
Total hardness =
𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽 𝑽𝑽𝒐𝒐 𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬 𝒔𝒔𝑽𝑽𝑽𝑽𝑽𝑽𝒔𝒔𝒔𝒔𝑽𝑽𝒔𝒔 𝒄𝒄𝑽𝑽𝒔𝒔𝒔𝒔𝑽𝑽𝑽𝑽𝑽𝑽𝒄𝒄 𝑿𝑿 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽 𝑽𝑽𝒐𝒐 𝒔𝒔𝒕𝒕𝑽𝑽 𝒕𝒕𝒉𝒉𝒉𝒉𝒄𝒄 𝒘𝒘𝒉𝒉𝒔𝒔𝑽𝑽𝒉𝒉 𝒔𝒔𝒉𝒉𝒕𝒕𝑽𝑽𝒔𝒔 ppm = …….ppm
Calculation of permanent hardness : ……….ml Volume of boiled water taken : ……….ml
Permanent hardness = 𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽 𝑽𝑽𝒐𝒐 𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬 𝒔𝒔𝑽𝑽𝑽𝑽𝑽𝑽𝒔𝒔𝒔𝒔𝑽𝑽𝒔𝒔 𝒄𝒄𝑽𝑽𝒔𝒔𝒔𝒔𝑽𝑽𝑽𝑽𝑽𝑽𝒄𝒄 𝑿𝑿 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽 𝑽𝑽𝒐𝒐 𝒔𝒔𝒕𝒕𝑽𝑽 𝒃𝒃𝑽𝑽𝒔𝒔𝑽𝑽𝑽𝑽𝒄𝒄 𝒘𝒘𝒉𝒉𝒔𝒔𝑽𝑽𝒉𝒉 𝒔𝒔𝒉𝒉𝒕𝒕𝑽𝑽𝒔𝒔 ppm = …….ppm
Calculation of temporary hardness : Temporary hardness of the given sample of water = Total hardness – Permanent hardness = ……….ppm
Result : The temporary hardness of the given water sample is ………ppm.
Precautions :
1. Prepare the standard solutions accurately and end titration with the change
of colour.
2. Avoid skin and eye contact with pH 10 buffer. In case of skin contact, rinse the area for several
minutes. For eye contact, flush eyes with water and seek immediate medical advice.
To determine chloride ion in a given water sample by Argentometric method (Mohr’s
method)
Mohr’s method:
In Mohr’s method, the determination of the end point is based on the formation of a second
precipitate which is coloured. The requirement here is that the second precipitate should have
solubility slightly greater than the precipitate between the analyte and the titrant. The indicator
used is sodium chromate and the second precipitate formed is brick–red coloured silver
chromate, Ag 2 CrO 4. Volume of 0.001 M AgNO 3 titrant, On the addition of a solution of silver
nitrate to the titrant (containing chloride ions the analyte and chromate ions-the indicator) two
precipitates are formed. These are AgCl and Ag2CrO4 respectively.
The reactions can be given as under
The silver chromate having greater solubility stays in solution whereas silver chloride
precipitates out. At the end point the excess of silver ions forms the precipitate of silver
chromate that imparts distinct colour to the solution thereby marking the end point. The titration
is carried out at a pH between7 to 10. This is so because in acidic solution the chromate ion
gets converted into chromic acid and the concentration of chromate ion becomes quite low. It
is not sufficient to precipitate the silver ions as silver chromate. On the other hand, at the pH
greater than 10 a brown precipitate of hydrated silver oxide is obtained. The pH is maintained
in the suitable range by adding sodium bicarbonate to the analyte solution The Mohr’s method
suffers with a drawback as it has an inherent titration error. The end point is not observed
immediately after the equivalence point but after a little over titration, i.e., after adding a little
extra silver nitrate. This necessitates the determination of an indicator blank. This is determined
by suspending solid, white, chloride–free calcium carbonate in distilled water and making the
volume as that of the titrated solution at the equivalence point. This would have the
concentration of CrO4 2– equal to that at the equivalence–point. The Ag+ reagent is added to
this suspension until the end point colour is observed. The volume of Ag+ reagent required to
match the end point colour is subtracted from the end point volumes measured in the titrations
of chloride.
Material Required :
- NaCl = 10ml (dil solution)
- CaCO 3
- NaHCO 3 = 10ml (dil solution)
- K 2 CrO 4 = 10ml (dil solution)
- AgNO (^3)
Procedure:
Wash the burette with distilled water and rinse with standardised solution of silver nitrate and
then fill the burette with the same.
