Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech I CHEMISTRY Previous Question Paper (November/December - 2020 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain various factors that influence the magnitude of crystal field stabilization energy in complex compounds.
Answer
The Crystal Field Stabilization Energy (CFSE) is influenced by several key factors:
- Nature of the Ligand: Ligands are arranged in the spectrochemical series based on their field strength. Strong-field ligands (e.g., CN⁻, CO) cause a large splitting (Δ), leading to higher CFSE, while weak-field ligands (e.g., I⁻, Cl⁻) cause small splitting.
- Oxidation State of the Metal Ion: As the oxidation state of the central metal ion increases, the metal-ligand bond becomes shorter and the electrostatic attraction stronger, resulting in a larger crystal field splitting energy.
- Geometry of the Complex: The magnitude of splitting depends on the coordination geometry. For instance, the splitting in octahedral complexes (Δo) is significantly larger than in tetrahedral complexes (Δt), where Δt ≈ 4/9 Δo.
- Principal Quantum Number of the Metal: Splitting increases as we move down a group in the periodic table (from 3d to 4d to 5d series) because the d-orbitals become more extended and interact more strongly with ligand orbitals.
Explain filling of electrons in F2 molecule in terms of Molecular orbital theory with neat diagram.
Answer
According to Molecular Orbital Theory (MOT), the F₂ molecule is formed by the overlap of two fluorine atoms, each with the electronic configuration 1s² 2s² 2p⁵. The total number of electrons is 18.
The molecular orbital energy level diagram for F₂ follows the order: σ1s < σ*1s < σ2s < σ*2s < σ2p_z < π2p_x = π2p_y < π*2p_x = π*2p_y < σ*2p_z.
Filling of electrons:
The bond order is calculated as:
Since the bond order is 1, F₂ contains a single covalent bond. The presence of all paired electrons indicates that the F₂ molecule is diamagnetic.
Explain the postulates of Molecular orbital theory.
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With the help of MO diagram, calculate bond order of O2 molecule and predict its magnetic behavior.
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How municipal water can be treated before distribution for the domestic purpose?
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Determine the temporary, permanent and total hardness in ppm units for a water sample from Warangal which showed the following analysis: Ca(HCO3)2 = 30.4 mg/litre; Mg(HCO3)2 = 30.2 mg/litre; NaCl = 5.85 mg/litre; CaCl2 = 20.2 mg/litre, MgSO4 = 11.2 mg/litre; Organic matter = 15.5 mg/litre.
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Describe the reverse osmosis process for desalination of brackish water with diagram.
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What is the process of Chlorination? What are the advantages? Explain the significance of breakpoint chlorination.
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Explain the following factors that can influence the rate of corrosion: i) specific volume ratio ii) Position in galvanic series iii) Humidity.
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Describe the construction and working of calomel electrode.
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Calculate the equilibrium constant for the following reaction at 298K. Cu + Cl2 → CuCl2 given E0(Cu+2/Cu) = 0.34 V and E0(Cl2/2Cl-) = 1.36 V.
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What is the principle involved in the cathodic protection? Discuss the sacrificial anodic and impressed current methods.
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Explain Markownikoff’s addition products in addition of HBr to propene.
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What are conformers? Discuss the conformational analysis with reference to n-Butane.
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Discuss various factors that influence chemical shift.
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Give an account of various modes of fundamental vibrations.
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