UPSC Civil Services (Mains)
Chemistry optional
- 2 papers
- 250 marks each
- 3 h per paper
- 5 of 8 questions, Q1 and Q5 compulsory
Paper I covers physical and inorganic chemistry.
All years

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Paper I, physical and inorganic chemistry
Solution, 2016
UPSC Civil Services (Mains), Chemistry optional. 46 pages. All eight questions are answered.
Every question of 2016, one page each37 parts in 8 questions, with the question as text and its full model answer
Question 1 50 marks
- 1(a)(i)Bond angles of CH₄, NH₃ and H₂O5 marks
- 1(a)(ii)Dipole moments of BF₃ and PF₃5 marks
- 1(b)Residual entropy of CO and N₂O10 marks
- 1(c)(i)Derivation of the Bragg equation5 marks
- 1(c)(ii)Spacing of the (110) planes of a cubic cell5 marks
- 1(d)Continuity of state: Andrews' isotherms of CO₂10 marks
- 1(e)Specific conductance of saturated BaSO₄10 marks
Question 2 50 marks
Question 3 50 marks
Question 4 50 marks
Question 5 50 marks
- 5(a)(i)Splitting of d orbitals in a square-planar field5 marks
- 5(a)(ii)CFSE and spin-only moment of [Co(NH₃)₆]Cl₂5 marks
- 5(b)Isomers of [CoCl₂(en)₂]⁺; is there a meso form?10 marks
- 5(c)Structure of Fe₂(CO)₉ and the 18-electron rule10 marks
- 5(d)Oxidative addition against insertion10 marks
- 5(e)Oxidation states of the lanthanides other than +310 marks
Question 6 50 marks
Question 7 50 marks













































