IGNOU MSCANCHEM MCH 4 SOLVED ASSIGNMENT

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MCH 4 2025 - English

Tutor Marked Assignment

MCH-004: Electroanalytical and Other Methods

Course Code: MCH-004

Assignment Code: MCH-004/TMA/2025

Maximum Marks: 100

Note: Answer all the questions given below.

1.

a) Derive the Nernst expression for galvanic cell.

b) What are the characteristics of a reference electrode? Describe the construction and working of a Calomel electrode.

2. 

a) What is meant by Ion Selective electrodes? Give their applications.

b) What is the cell potential of an electrochemical cell made of a cadmium electrode in a 0.1 M Cd(NO₃)₂ solution and chromium electrode in a 1 x 10 M Cr(NO₃)₃ solution.

[Given: ]

3. a) Write five main features of coulometric methods.

b) What are molar conductivity and limited molar conductivity? Calculate the dissociation constant of 0.02 mol dm^-3 ethanoic acid, if its molar conductivity is 11.57  10^-4 S m² mol^-1 and limited molar conductivity is 3.90 x 10^-2 S m² mol^-1 .

4. a) To analyse a brass alloy, a 0.442 g sample is dissolved in acid to volume in a 500 cm³ volumetric flask. Electrolysis of a 10 cm³ sample at -0.3 V vs SCE reduces Cu²⁺ to Cu, requiring total charge of 16.11 C. Adjusting the potential of 0.6 V vs SCE and completing the electrolysis requires 0.442 C to reduce Ph²⁺ to Pb. Report the percentage of Cu and Pb in the alloy.

b) What is stripping voltammetry? Taking a suitable example discuss the anodic  stripping voltammetry.

5. a) What are the factors affecting the diffusion current? Discuss these factors in brief.

b) How will you determine lead and copper in carbon steels using polarographic  method?

6. a) Discuss various sources of errors in TGA.

b) A mixture of CaCO3 and CaO is analysed using TGA method. TG curve of the sample indicates that there is a mass change from 290.6 mg to 230.8 mg between 500-900^.C. Calculate the percentage of CaCO3 in sample.

7. a) Write down any five applications of DSC technique.

b) Give the difference between thermometric and classical titrimetry.

8. a) Define the unit of radioactivity, Curie (Ci) and Becquerel (Bq). Calculate the  strength of 9.6 ng of ¹⁹⁸Au (t_1/2 = 2.7 d) in Curie.

b) A 0.5 cm³ solution containing 8.5 µCi of ⁵⁹Fe wasinjected into the blood stream of a horse. After equilibrium, 1.0 cm3 of blood was taken out and it gave 26448 counts in 6 minutes. Calculate the blood volume in the body of horse.

9. a) Discuss the important criteria for the choice of radiotracers. Name the isotop  used for the determination of Mn steel.

b) Explain methodology of radioimmunoassay and list its advantages.

10. Write short notes:

a) Ionic product of water

b) NAA

c) Square wave polarography

d) Ohmic potential

 

MCH 003 (July 2025 - January 2026) - ENGLISH

Tutor Marked Assignment

Electroanalytical and Other Analytical Methods (MCH-004)

Course Code: MCH-004

Assignment Code: MCH-004/TMA/2026

Maximum Marks: 100

Note: Answer all the questions given below.

1. a) Derive an expression for the determination of an equilibrium constant using electrode potential measurement. 

b) Calculate the potential of the cell given below
Cu|Cu²⁺ (0.010 M)||Ag⁺|Ag(0.10M)

Hint: use Appendix I for the standard electrode potential values.

2. a) How is the conductance varied with concentration? Explain with the help of suitable examples. 

b) At 298 K, the limited molar conductivities at infinite dilution of sodium benzoate, hydrochloric acid and sodium chloride are 8.24 × 10⁻³ S m² mol⁻¹, 4.26 × 10⁻² S m² mol⁻¹ and 1.26 × 10⁻² S m² mol⁻¹, respectively. Calculate the limiting molar conductivity of aqueous benzoic acid. 

3. a) Discuss the factors which limit the accuracy of pH measurements. 

b) Give two applications of ion selective electrodes. 

4. a) Describe concentration polarization. Give the importance of overvoltage. 

b) A solution of Zn is electrolyzed for 30 s using a current of 1.0 mA. Calculate the mass of Zn plated on the electrode for the electrochemical reaction:
Zn²⁺ + 2e⁻ → Zn 

5. a) Write the advantages of coulometric titrations. 

b) Calculate the amount of Co (II) deposited on the surface of a cathode, if a constant current of 0.96 A for 28.4 minutes is passed through solution of Co (II). Assume that current efficiency is 90%. 

6. a) Conductivity of 1.6 × 10⁻² mol dm⁻³ acetic acid is 0.0215 S m⁻¹. Calculate the degrees of dissociation and the dissociation constant of acetic acid. You may consult Table 4.2 for the limiting ionic conductivities of the hydrogen and acetate ion. 

b) How would you analyze a mixture of Ca, Sr, and Ba oxalates using thermogravimetry? Draw a thermogram for the decomposition of Ca, Sr and Ba oxalates.

7. a) List the advantages of DTA and DSC over TGA. 

b) An impure sample of CaC₂O₄·H₂O is analyzed using TGA technique. TG Cure of the sample indicates the total mass change from 85 mg to 30.7 mg when this sample was healed up to 900° C. Calculate the % purity of the sample. 

8. a) Draw a DTA Curve for CaC₂O₄·H₂O. Give the interpretations of different peaks exist in the thermogram. 

b) At 291 K, the conductivity of pure water is 4.3×10⁻⁶ S m⁻¹. Calculate the ionic product of pure water at 291 K. 
Hint: consult Table 4.2 for the limiting ionic conductivity of H⁺ and OH⁻ ions.

9. a) Give advantages and limitations of NAA technique. 

b) Discuss the working of a Scintillation Detector. 

10. a) Draw and label the three-electrode cell for hydrodynamic voltammetry. 

b) Write the Ilkovic equation and mention the meaning of each of the terms used in it. 

 

MCH 004 (January 2026) - ENGLISH

TUTOR MARKED ASSIGNMENT

ELECTROANALYTICAL AND OTHER METHODS

Course Code: MCH-004

Assignment Code: MCH-004/TMA/2026

Maximum Marks: 100

Note: Answer all the questions given below.

Q.1

a) What do you understand by cell potential? Calculate the potential of following electrodes:

i) A copper electrode immersed in 0.022 M Cu (NO3)2

ii) A zinc electrode immersed in 0.030 M Zn (NO3)2

b) Describe various factors that cause errors in pH measurement.

Q.2

a) What is solid state membrane electrode? Draw a sketch and describe their applications.

b) Define conductivity, cell constant and molar conductivity.

Resistance of a conductivity cell filled with 0.1M KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 M KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 M KCl solution. The conductivity of 0.1 M KCl solution is 1.29 Sm¹.

Q.3

a) How will you analyse a binary alloy of copper and silver thermogravimetrically.

b) A solution of CuSO4 is electrolysed for 10 minutes with a current of 1.5 amperes. What is the mass of copper deposited at the cathode?

Q.4

a) Explain how will you determine dissociation constant of a weak acid or base by conductometric method.

b) The conductivity of 0.001028 M acetic acid is 4.95 × 105 S cm²¹. Calculate its dissociation constant if the limited molar conductivity for acetic acid is 390.5Scm² mol¹.

Q.5

a) Describe the design and principle of constant current coulometry. Write three main applications of coulometric titrations.

b) Enlist various voltammetric methods of analysis. Write briefly about anodic stripping voltammetry(ASV) and its usefulness for trace elemental analysis.

Q.6

a) Explain the terms limiting current, migration current, diffusion current, residual current and half wave potential.

b) What is dropping mercury electrode? Give its advantages.

Q.7 a) What are amperometric titrations? Draw common types of curves obtained in amperometric titrations. Briefly discuss their experimental set up.

b) List the factors affecting TG curve. Taking a suitable example, explain the effect of furnace atmosphere on TG curve.

Q.8

a) Draw a labelled diagram of the TG curve obtained by heating a mixture of 50 mg of calcium oxalate monohydrate and 50 mg of barium oxalate monohydrate to 1200°C. Calculate the amount of all mass losses.

b) Explain the basic principle of Differential Scanning Calorimetry (DSC). Draw a block diagram of DSC instrument.

Q.9 

a) Describe various types of neutron sources available for NAA. Which one of these is most suitable for trace element analysis?

b) In what respects nuclear reactions are different from chemical reactions? Calculate Q value of the reaction 63Cu = (η, γ) 64 Cu. Give that Cu = 62.929590, Cu = 64, 63.929760, n =1.008665 amu.

Q.10

a) Explain why (n, y) reaction is most suited for NAA.

b) Discuss the principle of isotope dilution technique.

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