1 . ESTIMATION OF FERROUS ION BY CERIMETRY Titration I: Standardisation of Cerium (IV) sulphate solution: S. No. Volume of Std FeSO4 (ml) Burette reading (ml) Volume of CAS (ml) Initial Final Calculation : Volume of FeSO4 = Normality of FeSO4 = Volume of CAS = Normality of CAS =--------------------N.
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1 . ESTIMATION OF FERROUS ION BY CERIMETRY
Titration I: Standardisation of Cerium (IV) sulphate solution:
S. No.
Volume of Std FeSO4
(ml)
Burette reading (ml) Volume of CAS
(ml)Initial Final
Calculation :Volume of FeSO4 =
Normality of FeSO4 =
Volume of CAS =
Normality of CAS =--------------------N.
1. ESTIMATION OF FERROUS ION BY CERIMETRY
Exp. No: Date:
Aim:To estimate the amount of ferrous ion present in the whole of the given solution.A standard solution of
0.01N ferrous ammonium sulphate and an approximately 0.01N solution of Ceric ammonium sulphate are
supplied.
Principle:Ceric ions oxidise ferrous ions in acid medium according to the equation,
Ce+4+Fe+2→Ce3++Fe+ 3
The ceric ammonium sulphate solution of approximately known strength is standardized against
standard FAS.
For the above titrations, redox indicator ferroin can be used. Ferroin is a complex formed between
Fe(II) ion and 1,10-phenanthroline, [Fe(Phen)3]+2. The reduced form of indicator has an intense red colour,
whereas oxidised iron (III) complex has a blue colour. The indicator reaction may be written as,
[Fe (Phen )3 ]3++c [Fe (Phen )3 ]
+2
Pale blue Red
When iron (II) is titrated with Ce (IV) in sulphuric acid medium, the ferroin indicator is initially red in
colour in its reduced form.At the end point, Ce (IV) oxidises it to Fe (III) complex. The end point, is a sharp
change from red to pale blue colour.
Titration I: Standardisation of Cerium (IV) sulphate solution:Pipette out 20ml of Ferrous ammonium sulphate solution in to a clean conical flask. Add about 20ml of
2N sulphuric acid followed by 2 drops of ferroin indicator. Titrate it against Cerium (IV) solution taken in the
burette. The end point is colour change from red to pale blue colour. Repeat the titration to get concordant
value. From the titre value, calculate the strength of cerium (IV) solution.
Titration II: Estimation of Ferrous ionMake up the given ferrous ion solution to 100ml in a standard flask. Pipette out 20ml of this solution in to
a clean conical flask. Add about 20ml of 2N sulphuric acid solution and 2 drops of ferroin indicator. Titrate it
against standardised cerium (IV) solution taken in the burette. End point is colour change from red to pale blue
colour. Repeat the titration to get concordant value. From the titre value, calculate the strength of ferrous ion
and hence calculate the amount of ferrous ion present in the given solution.
Titration II: Estimation of Ferrous ion
S. No.
Volume of FeSO4
(ml)
Burette reading (ml) Volume of
CAS(ml)Initial Final
Calculation
Volume of CAS =
Normality of CAS =
Volume of FeSO4 =
Normality of FeSO4 = --------------------N.
The amount of Ferrous present in the whole of given solution =(Normality x Eq.Wt)/10
=----------------------g.
Result:The amount of ferrous ion present in the whole of the given solution = ___________g.
Experiment No.: 2 Date:…………
Objective: Determine the concentration of KMnO4 solution SpectrophotometricallyApparatus Required: UV- Visible spectrophotometer, cuvette, test tubes, pipette
Chemical required: KMnO4
Principle: When an electromagnetic radiation is passed through a sample, certain characteristic wavelengths are
absorbed by the sample as a result the intensity of the transmitted light is decreased. The measurement of the
decrease in intensity of the radiation is the basis of spectrophotometry.
The lmax of KMnO4 solution is calculated by plotting the graph in between the absorbance (A) and
wavelength and the concentration of the KMnO4 solution is calculated by plotting the graph in between the
absorbance (A) and concentration of the solution.
The relationship between absorbance and transmittance is illustrated in the following diagram:
Fig. 1
Significance:
UV / Visible spectrophotometers are used in the modern life science laboratory for the quantification of
nucleic acids, the determination of protein concentrations and the calculation of enzyme activity in kinetics
studies.
The purity of DNA and RNA extractions from cells can be readily measured using spectrophotometry
Procedure:
1. Switch ON the instrument and allow it to self calibrate.
2. Set the instrument as per the direction given by the instructor.
3. Prepare the solution of different concentrations from the given stock solution.
4. Note down the value of absorbance for different concentration of KMnO4 solution at 440 nm
wavelength (say 0.5%, 1.0%, 1.5%, 2.0% etc.)
5. Plot the observed values of absorbance against concentration.
6. Find the concentration of given unknown KMnO4 solution from the plotted graph.
Observation:
Determination of concentration of given KMnO4 solution
Sr. No. Concentration (C) Absorbance (A)
1.
2.
3.
4.
5.
6.
Unknown
Absorbance
Concentration
Graph in between absorbance and Concentration
Result:
Concentration of given KMnO4 = mg/l
Precautions:
1.Always use the dilute solution.
2. Cuvette should be cleaned properly and must be wiped with tissue paper.
3.Do not leave any finger marks on the cuvette.
Questions:
1. What is the purpose of this experiment? What is the relation between concentration and absorbance?
2. Mention the role of potassium permanganate in the water treatment.
3. What is the light source for visible region and UV region of the spectrum?
4. What are the advantages of using Quartz or silica cells over Glass and plastic when
measuring absorption of ultraviolet wavelengths by a solution?
5. Why is it important to determine lmax before determine the concentration of the
unknown?
3. ESTIMATION OF NICKEL IN AN ALLOY BY COMPLEXOMETRY
Exp. No: Date:
Aim:To estimate the amount of Nickel present in the whole of the given nickel alloy solution. A standard
solution of 0.01N Nickel sulphate and an approximately 0.01N EDTA solution are supplied.
Principle:
Nickel can be estimated by using EDTA as titrant and murexide as indicator. Murexide form complexes
with nickel at pH 11. Murexide is the ammonium salt of Purpuric acid. The colour change in the direct titration of
nickel at pH 10 – 11 is from yellow to bluish violet.
Procedure:Titration I: Standardisation of EDTA
Pipette out 20ml of standard nickel sulphate solution into a clean conical flask. Add a pinch of Murexide
indicator , and 10ml of 1M ammonium chloride solution and then add concentrated ammonia solution drop wise
till the pH is about 7 as shown by yellow colour of the solution. Titrate the mixture in conical flask against EDTA
taken in burette until colour changes from yellow to violet. (Nickel complexes rather slowly with EDTA and
consequently the EDTA solution must be added drop wise near the end point). Repeat the titration to get
concordant value. From the strength of Nickel sulphate solution calculate the strength of EDTA.
Titration II: Estimation of Nickel Transfer the given nickel alloy solution into a clean 100ml standard flask quantitaively and make upto
the mark using distilled water. Pipette out 20ml of made up nickel alloy solution into a clean conical flask. Add a
pinch of Murexide indicator and 10ml of 1M ammonium chloride solution and then add concentrated ammonia
solution drop wise till the pH is about 7 as shown by yellow colour of the solution. Titrate the mixture against
standardised EDTA taken in burette until colour changes from yellow to violet. Repeat the titration to get
concordant value. Calculate the strength of nickel solution by using strength of EDTA and hence the amount of
nickel present in the given solution.
Titration II: Estimation of Nickel
S. No. Volume of Nickel Sulphate
(ml)
Burette reading (ml) Volume of
EDTA(ml)Initial Final
Calculation
Volume of EDTA =
Normality of EDTA =
Volume of NiSO4 =
Normality of NiSO4 =--------------------N
The amount of Nickel present in the whole of given solution =(Normality x Eq.Wt)/10
=----------------------g.
Result:The amount of nickel present in the whole of the given solution = g.
Experiment No……4….. Date:…………….
Objective: To determine the concentration of iron in water sample by spectrophotometric method.
Theory: The formation of silver nanoparticles can be observed by a change in color since small nanoparticles of silver are yellow. Sodium borohydride is used as a reducing agent and a layer of absorbed borohydride anions on the surface of the nanoparticles keep the nanoparticles separated. PVA acts as stabilizing agent. The scattering of light caused by spherically shaped colloidal silver nanoparticals shows golden yellow colour. When sodium cholride (NaCl) is added the nanoparticles aggregate and the suspension turns cloudy gray. The addition of a small amount of polyvinyl pyrrolidone will prevent aggregation.
Nanotechnology deals with processes that take place on the nanometer scale, that is, from approximately 1 to 100 nm. Properties of metal nanoparticles are different from those of bulk materials made from the same atoms. For example, silver metal is grayish,but colloidal silver from this synthesis is a clear yellow. The striking effect of nanoparticles on color has been known since antiquity when tiny metal particles were used to color glass in church windows. Silver particles stained the glass yellow, while gold particles were used to produce ruby glass.
Synthesis of Colloidal Ag
Colloidal silver is made by adding an excess of the reducing agent sodium borohydride, NaBH4 to silver nitrate, AgNO3. Particle size can also be determined using visible spectroscopy.
AgNO3 + NaBH4 Ag + 1/2H2 + 1/2B2H6 + NaNO3
Characterization of Colloidal Ag
Sample has to be characterized by UV spectroscopy. The presence of metal in the solution is related to a broad absorbance peak at 410 nm.The height of peak gives information about the metallic compound concentration in the medium. For the 12 nm Ag nanoparticles, the maximum wavelength is near 400 nm. In general, as the particles become larger the absorption maximum shifts to longer wavelengths.
When an electromagnetic radiation is passed through a sample, certain characteristic wavelengths are absorbed by the sample as a result the intensity of the transmitted light is decreased. The measurement of the decrease in intensity of the radiation is the basis of spectrophotometry.
The lmax of solution is calculated by plotting the graph in between the absorbance (A) and wavelength and the concentration of the solution is calculated by plotting the graph in between the absorbance (A) and concentration of the solution. Size and shape dependent colors of Au & Ag nanoparticles are shown in the table.
Procedure: 1.Take 1mL of 0.001M silver nitrate (AgNO3) and make it up to 10 mL.
2.Add 1mL of polyvinyl alcohol (PVA) 1% solution to the beaker slowly with constant stirring.3.Add a magnetic stir bar and place the flask on a stir plate and further add 40 mL of 0.0001M sodium borohydride (NaBH4) to above solution slowly with constant stirring.and and cool the liquid for about 20 minutes.4.Switch on the spectrophotometer and allow it to self calibrate.5.Take spectra to find a broad absorbance peak at 410 nm.
Result: Colour of silver nanoparticals:Shape of silver nanoparticals:Size of silver nanoparticals:
Precautions:1. Costant stirring should be done.2. Cuvette should be cleaned properly and must be wiped with tissue paper.3.Do not leave any finger marks on the cuvette.
Safety and Waste Disposal: Safety glasses are always required in the laboratory.Gloves must be worn throughout this experiment. Silver nitrate is caustic and stains theskin. A container will be made available for any waste solutions.
CAUTION: Stop the stirring as soon as the silver nitrate solution is added and remove the stir bar. If the stirring is continued once all the silver nitrate has been added,aggregation is likely to occur; the yellow darkens, turns violet, then grayish as the particles settle out.
The product should be clear yellow once the reaction is completed and should remainyellow, although it may darken somewhat. Record the appearance of your product assoon as the stirring is stopped and after waiting for about 5 minutes. If your product hasaggregated and turned gray---repeat the synthesis if possible.
Questions:1. What is the purpose of this experiment? What is the relation between concentration and absorbance? 2. Mention the colour, size and shape of nanoparticals of silver and gold.3. What are the main applications of silver and gold nanoparticals. 3. What is the light source for visible region and UV region of the spectrum?4. What are the advantages of using Quartz or silica cells over Glass and plastic when measuring absorption of ultraviolet wavelengths by a solution?5. Why is it important to determine lmax before determine the concentration of the unknown?