MCH-022 Solved Assignment January 2026 | SEPARATION AND SPECTROSCOPIC METHODS | IGNOU MSCCHEM

Q: Attempt both sub-parts.

Answer available — download the full PDF for complete details.

Q: Attempt both sub-parts.

Answer available — download the full PDF for complete details.

Q1. Attempt both sub-parts.

(a)) Briefly discuss the extraction of metal ions using crown ethers. (200 words)
(b)) Giving suitable examples, discuss the role of masking agents in extractions. (200 words)

Key Points:

Crown ethers are macrocyclic polyethers that selectively complex metal ions.
Crown ether cavity size matches ion radius for selective host-guest complexation and extraction.
Metal-crown ether complex becomes lipophilic, enabling transfer to organic phase.
Masking agents prevent interfering ions from co-extracting with the target analyte.

Answer: Separation and spectroscopic methods are crucial in analytical chemistry for isolating and identifying components in a mixture. Extraction, a key separation technique, often faces challenges like low selectivity or interference from co-existing ions. This necessitates advanced approaches like the use of crown ethers for specific metal ion extractions and masking agents to prevent unwanted interferences. Crown ethers provide a highly selective means of extracting metal ions by forming stable, li...

Q2. Attempt both sub-parts.

(a)) What are the characteristics of stationary phases used in liquid-solid chromatography? Discuss various types of adsorbents used. (200 words)
(b)) Give any five comparisons between PC and TLC. (200 words)

Key Points:

LSC stationary phases require high surface area, porosity, inertness, and mechanical strength.
Silica gel, a weakly acidic adsorbent, is widely used in LSC, with strength modifiable by water content.
Alumina is another LSC adsorbent, available in acidic, basic, and neutral forms for diverse separations.
PC uses cellulose paper with adsorbed water as stationary phase; TLC uses an adsorbent layer on a plate.

Answer:

Q3. Attempt both sub-parts.

(a)) Give a brief account of various injection systems used in gas chromatography. (200 words)
(b)) Draw a schematic diagram of an HPLC instrument and also list the components. (200 words)

Key Points:

GC injection systems introduce sample into the column, choices include Split/Splitless, On-column, PTV, and Headspace.
Split/Splitless GC injector uses split mode for concentrated samples and splitless for trace analysis.
On-column injection in GC prevents thermal degradation for heat-sensitive samples by direct column injection.
HPLC instrumentation includes mobile phase reservoir, pump, injector, column, detector, and data system.

Answer:

Q4. Attempt both sub-parts.

(a)) Discuss the use of hydrous oxides of polyvalent metals as synthetic ion exchangers giving suitable examples. (200 words)
(b)) Describe the unique features of size exclusion chromatography. (200 words)

Key Points:

Hydrous oxides of polyvalent metals are synthetic inorganic ion exchangers.
They are amphoteric, exchanging cations in alkaline and anions in acidic conditions.
Examples include hydrous zirconium oxide and hydrous thorium oxide.
Size exclusion chromatography (SEC) separates molecules by hydrodynamic volume.

Answer: The provided question delves into two distinct but important aspects of separation science within MCH-022: the role of inorganic materials as ion exchangers and the unique mechanism of size exclusion chromatography. Part (a) focuses on the chemical properties and applications of hydrous oxides of polyvalent metals in ion exchange, highlighting their amphoteric nature and stability. Part (b) elaborates on size exclusion chromatography, emphasizing its principle of separation by molecular size, th...

Q5. Attempt both sub-parts.

(a)) Discuss the applications of membrane separations in (i) water treatment (ii) production of table salt (200 words)
(b)) Give important aspects of capillary electrochromatography. (200 words)

Key Points:

RO in water treatment desalinates, removes heavy metals, and microbes for potable water.
UF/MF pre-treat water by removing suspended solids, bacteria, and large organic matter.
RO concentrates brine for table salt production, reducing energy for subsequent evaporation.
CEC combines capillary electrophoresis (EOF) with liquid chromatography (stationary phase).

Answer: Membrane separations are advanced techniques used for purifying and concentrating substances by selectively passing certain components through a semi-permeable barrier. Capillary electrochromatography (CEC) is a powerful hybrid analytical method that combines the principles of chromatography and electrophoresis to achieve high-resolution separations.

Q6. Attempt both sub-parts.

(a)) Explain the nature of absorption spectra for the transition and inner transition elements by UV-Vis spectroscopy. Also specify the reasons of difference between the two. (200 words)
(b)) What are the advantages of UV-Vis spectrometry for quantitative determinations? Write the steps involved in the quantitative determinations using this technique. (200 words)

Key Points:

Transition elements show broad, weak d-d UV-Vis bands, highly ligand-sensitive.
Inner transition elements exhibit sharp, narrow, intense f-f UV-Vis bands, ligand-insensitive.
Difference stems from shielding of f-orbitals vs. direct ligand interaction with d-orbitals.
UV-Vis quantitative analysis is sensitive, rapid, inexpensive, and non-destructive.

Answer: UV-Vis spectroscopy provides distinct absorption spectra for transition and inner transition elements, primarily due to differences in their electronic transitions and the shielding of their valence orbitals from the external environment. Quantitative determinations using this technique are advantageous for their sensitivity and rapidity, following a well-defined series of steps based on the Beer-Lambert Law. Transition elements (d-block) exhibit broad and relatively weak absorption bands resul...

Q7. Attempt both sub-parts.

(a)) How does FTIR differ from traditional dispersive IR spectrometry? Write any four advantages of the FTIR spectrometry. (200 words)
(b)) What are the two aspects in which fluorimetry differs from phosphorimetry? Describe the aspects. (200 words)

Key Points:

FTIR uses an interferometer and Fourier Transform; dispersive IR uses a monochromator for sequential scanning.
FTIR offers Fellgett's (multiplex), Jacquinot's (throughput), and Connes' (accuracy) advantages.
Fluorimetry involves emission from a singlet excited state (S₁), a spin-allowed, rapid process.
Phosphorimetry involves emission from a triplet excited state (T₁), a spin-forbidden process after intersystem crossing.

Answer: The field of spectroscopic methods is crucial for chemical analysis, enabling the identification and quantification of various substances. This question delves into key differences and advantages within infrared spectroscopy, contrasting modern FTIR with traditional dispersive methods, and then explores the distinctions between two significant luminescence techniques: fluorimetry and phosphorimetry. Understanding these differences is fundamental to selecting appropriate analytical tools for dive...

Q8. Attempt both sub-parts.

(a)) List the characteristics of atomisation-excitation source in atomic emission spectrometry. Name the three types of plasma sources. (200 words)
(b)) Describe the principle of FT-NMR spectroscopy. Explain how is this spectroscopy advantageous over the CW-NMR spectroscopy. (200 words)

Key Points:

AES atomization-excitation sources require high temperature, stability, and efficient excitation with low background.
Three plasma sources in AES are Inductively Coupled Plasma (ICP), Direct Current Plasma (DCP), and Microwave Induced Plasma (MIP).
FT-NMR excites all nuclei simultaneously with a broad RF pulse, generating a time-domain Free Induction Decay (FID).
Fourier Transform converts the FID signal from the time domain to a frequency-domain NMR spectrum.

Answer: The field of analytical chemistry relies heavily on spectroscopic methods for identifying and quantifying various substances. Atomic Emission Spectrometry (AES) and Nuclear Magnetic Resonance (NMR) spectroscopy are two distinct yet powerful techniques covered in MCH-022. AES focuses on the light emitted by excited atoms, requiring efficient atomization and excitation sources. NMR, particularly FT-NMR, investigates the magnetic properties of atomic nuclei to elucidate molecular structures, offeri...

Q9. Attempt both sub-parts.

(a)) What is DEPT in 13C NMR spectroscopy? Describe the features of its various types. (200 words)
(b)) List the limitations of 1D NMR spectroscopy. How does 2D NMR help in fulfilling the limitations? (200 words)

Key Points:

DEPT differentiates CH₃, CH₂, CH, and quaternary carbons in ¹³C NMR spectra.
DEPT-90 shows only methine (CH) carbons as positive signals.
DEPT-135 displays CH and CH₃ as positive, CH₂ as negative signals, with quaternary carbons absent.
1D NMR limitations include signal overlap and complex coupling pattern interpretation.

Answer:

Q10. Attempt both sub-parts.

(a)) What are the two types of ion sources used in mass spectrometry? Explain these sources. (200 words)
(b)) Compare GC-MS and LC-MS and LC-MS with reference to the sample types and the solvents used. (200 words)

Key Points:

Electron Ionization (EI) is a "hard" MS source for volatile, thermally stable compounds, yielding fragment ions for structural information.
Electrospray Ionization (ESI) is a "soft" MS source for non-volatile, thermally labile molecules, producing intact protonated/deprotonated ions.
GC-MS analyzes volatile, thermally stable compounds using a gas carrier and typically EI for fragmentation.
LC-MS analyzes non-volatile, polar, thermally labile compounds using a liquid mobile phase and soft ionization (e.g., ESI).

Answer:

MCH-022 Solved Assignment — January 2026 / July 2025

SEPARATION AND SPECTROSCOPIC METHODS | IGNOU Master of Science in Chemistry Programme (MSCCHEM)

MCH-022—January 2026 / July 2025

SEPARATION AND SPECTROSCOPIC METHODS

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MCH-022 Assignment Questions — January 2026

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Q3. Attempt both sub-parts.

Q4. Attempt both sub-parts.

Q5. Attempt both sub-parts.

Q6. Attempt both sub-parts.

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Q10. Attempt both sub-parts.