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IGNOU MCH-25 (July 2025 – June 2026) Assignment Questions
1. (a) Give a difference between:
(i) oxidation and oxidizing agent
(ii) reduction and reducing agent
(iii) a galvanic cell and an electrolytic cell
(iv) voltammetry and polarography
(b) Consider the following electrochemical cell
2. (a) What is Coulometer? Explain briefly. Write cathodic and anodic reaction of hydrogen-nitrogen coulometer, where 0.1 M hydrazine sulphate is used as the electrolyte.
(b) In a coulometric method, 200 mg of nitrobenzene in 100 cm3 of methanol is reduced to phenyl hydroxylamine at a constant potential of -0.95 V (vs. SCE) applied to an Hg electrode. Following reaction takes 30 minutes to complete.
3. (a) What is dropping mercury electrode? Give its advantages.
(b) Indium and Cadmium ions in 0.1 M HCl give peaks at potentials -0.557 V and -0.597 V by differential pulse polarographic analysis. When a standard solution containing 0.4 ppm of indium is analysed, it gave peak current (in arbitrary units) corresponding to 100.25 at -0.557 V and 43.75 at -0.597 V. A standard solution containing 0.4 ppm of Cd gave i ps 29.52 at -0.557 V and 64.8 at -0.597 V. What is the concentration of indium and cadmium in a sample if the peak current is 190 at -0.557 V and 120 at -0.597 V.
4. (a) What are amperometric titrations? Draw common types of curves obtained in amperometric titrations. What will be the shape of the curve in bioamperometry for the titration of iodine by thiosulphate?
(b) What is common source of errors in thermogravimetric analysis (TGA)? A mixture of CaO and CaCO3 is analysed by TGA. The result indicates that mass of the sample decreases from 250.6 mg to 190.8 mg only between 600°C and 900°C. Calculate the percentage of calcium carbonate in the mixture.
5. (a) Explain how thermometric titrations are different than classical titrations. Discuss their advantages.
(b) What is the principle of differential scanning calorimetry (DSC)? Draw theschematic diagram of a DSC instrument.
(b) What are the common sources of neutron for neutron activation analysis (NAA)? What factors contribute to higher sensitivity in NAA? Briefly explain anyone.
7. (a) Explain why neutron induced reactions are most common whereas deuteron induced reactions require accelerator facility to carry out these reactions.
(b) In an isotope dilution analysis experiment, 15 mg radiolabelled analyte with specific activity 0.57 μCi/mg was added. After equilibration and chemical separation 2.76 mg pure analyte having specific activity 0.019 μCi/mg was isolated. Calculate the amount of analyte in the sample.
8. (a) What is the difference between SEM and TEM? Write the advantages of TEM over SEM?
(b) Which components are used in the X-ray photoelectron spectroscopy (XPS)instrument? Briefly explain with a schematic diagram of XPS Instrumentation.
9. (a) What information does the energy dispersive spectroscopy (EDS) provide? Write any three applications of EDS.
(b) Briefly explain the basic principle of Auger Electron Spectroscopy (AES) with a suitable diagram.
10. (a) Write the basic principle of Rutherford backscattering spectroscopy (RBS) also name the ions commonly used for primary beam in RBS.
(b) How does atomic force microscopy (AFM) work? Explain briefly with their applications.
