CSS 2021 Chemistry Combined Papers Past Paper

Paper details

Examination

CSS

Year

2021

Subject

Chemistry

Paper

Combined Papers

Subject type

Optional

Mode

Subjective

Questions recorded from this paper

These 12 question wordings are transcribed from CSS Vista’s structured Chemistry past-paper record for CSS 2021.

1. Q4 · probability density(a) Explain photoelectric effect and probability density. (10) (b) (i) Explain Eigen function & Eigen value. (05) (10) (20) (ii) Derive Schrödinger wave equation for a particle in one dimensional box. (05)
2. Q8 · electrochemical seriesWrite notes on the following:- (i) Debye-Huckel theory. (07) (ii) Nernst’s equation. (07) (iii) Electrochemical series. (06) (20)
3. Q5 · thermochemistry(a) Predict molecular shapes using Valence Shell Electron Pair Repulsion (VESPER) (10) model. (b) (i) Explain the experimental techniques for determination of order of reaction. (05) (10) (20) (ii) Write a note on thermochemistry and calorimetry. (05)
4. Q6 · Gibbs Helmholtz equation(a) Derive a relation for dependence of Gibbs free energy on temperature or Gibbs (07) Helmholtz equation. (b) What is isothermal process? Explain work done in isothermal reversible expansion of (07) an ideal gas. (c) Explain fugacity and activity. (06) (20)
5. Q2 · Factors affecting rate of a chemical reaction(a) Explain applications of Schrodinger wave equation to hydrogen and hydrogen (10) like Atom. (b) (i) Give Molecular interpretation of entropy. (05) (10) (20) (ii) Explain factors affecting the rate of a chemical reactions. (05)
6. Q7 · common ion effect and their industrial applications(a) Discuss common ion effect and its industrial applications in detail. (08) (b) Describe significance of pka, pkb, pH. (06) (c) Write a note on basic concepts of chemical equilibrium. (06) (20)
7. Q3 · Valence bond theory (VBT)(a) What are the uses of chelates. (07) (b) State and explain Nomenclature of coordination complexes. (07) (c) Explain VBT (Valence Bond Theory) of coordination complexes in detail. (06) (20)
8. Q4 · Effect of substituents on orientation and reactivity(a) Write down reagents, reaction conditions and important steps for the following (10) conversions: (i) Chlorobenzene to 2,4-dinitrophenyl hydrazine (ii) Pyridine to 2-amino pyridine (b) Write a note that substituents on aromatic rings dictate reactivity and orientation of the (10) (20) incoming electrophile in electrophilic aromatic substitution reactions.
9. Q6 · Chemistry of Functional GroupsAccount for the following: (05 marks each) (20) (i) In DNA, a guanine residue reacts with electrophiles predominantly at the 7 and 3 positions of the ring system (see below). Suggest an explanation for this. (ii) Outline the synthesis of following compound: (iii) A Grignard reagent that is a key intermediate in an industrial synthesis of vitamin A can be synthesized in the following way: Wh at are the stru ctu res of compounds A and C? The acid catalysed rearrangement of A to B takes p1. (iv) What are compounds A and B in the reaction given below? Compound B has a strong IR absorption band in the 1650–1730 cm−1 region and a broad strong band in the 3200–3550 cm−1 region. 1. OsO4 CrO3 1-Methylcyclohexene A (C7H 14O2) B (C7H 12O2) 2. NaHSO3 CH3CO2H
10. Q3 · Aliphatic nucleophilic substitution and elimination reactions(a) Give the products expected (if any) when ethylbenzene reacts under following conditions: (i) Br2 in CCl4 (dark) (02 marks each) (10) (ii) HNO 3 ,H2 SO 4 (iii) Conc. H2 SO 4 (iv) (v) Alkaline KMnO 4 (b) Account for the following: (05 marks each) (10) (20) (i) Intramolecular H-bonding is stronger than intermolecular H-bonding (ii) Control of nucleophilic substitution reaction over elimination reactions
11. Q2 · S configuration and(a) Describe factors that influence keto-enol tautomerization. Elaborate the statement with the (10) help of examples. (b) Assign “R” or “S” configuration on each of the chiral centers of the given compounds. (10) (20)
12. Q7 · 1H NMRExplain the following: (04 marks each) (20) (i) How can IR be used to help interpret NMR spectra? (ii) What are diastereotopic protons? Explain with examples. (iii) Determine the structure for a compound with formula C 6 H4 N2 O4 with following H-NMR data:   8.76 t (1H), 8.38 dd (2H), 7.97 t (1H) (iv) Assign chemical shifts of each proton in the above structure. (v) Why 13 C-NMR is less sensitive than 1 H-NMR?

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