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
Question paper, 2024
UPSC Civil Services (Mains), Chemistry optional. 15 pages, as issued by UPSC.
Every question of 2024, one page each47 parts in 8 questions, with the question as text and the key points of its answer
Question 1 50 marks
- 1(a)(i)Most probable distance of the 1s electron5 marks
- 1(a)(ii)Lattice energies of NaBr and NaI above the calculated values5 marks
- 1(b)(i)Separation factor for ²³⁵UF₆ and ²³⁸UF₆ in one effusion stage5 marks
- 1(b)(ii)Unit cell and the cubic Bravais lattices5 marks
- 1(c)Normal boiling point of mercury10 marks
- 1(d)(i)Will CCl₂F₂ condense at 18 atm and 20 °C?5 marks
- 1(d)(ii)Overvoltage and its applications5 marks
- 1(e)Temperature at which the uncatalysed reaction matches catalase at 20 °C10 marks
Question 2 50 marks
Question 3 50 marks
- 3(a)(i)Viscosity of air at 298 K and at 0 K10 marks
- 3(a)(ii)Boyle temperature of Ar, CH₄ and C₆H₆5 marks
- 3(b)(i)Surface tension: ethanol or dimethyl ether5 marks
- 3(b)(ii)Pressure difference across a water droplet of radius 150 nm5 marks
- 3(c)(i)Change in Helmholtz energy on reversible isothermal compression10 marks
- 3(c)(ii)Why a tyre gets hot when it is pumped5 marks
- 3(c)(iii)Pressure of O₂ over NiO at 25 °C5 marks
- 3(c)(iv)Final temperature after Joule–Thomson expansion5 marks
Question 4 50 marks
- 4(a)Triple point, stable phase and enthalpy of sublimation of a new drug15 marks
- 4(b)(i)Polarography and concentration polarisation15 marks
- 4(b)(ii)Concentration cells; fuel cells as energy converters5 marks
- 4(c)(i)Time of maximum concentration of B in A → B → C10 marks
- 4(c)(ii)Yield of P₁ from three parallel paths5 marks
Question 5 50 marks
- 5(a)Fluorescence and phosphorescence on a Jablonski diagram10 marks
- 5(b)(i)How water condenses onto glass5 marks
- 5(b)(ii)Time to form half a monolayer at 2.0 × 10⁻¹¹ torr5 marks
- 5(c)IUPAC names of five complexes10 marks
- 5(d)Zeise's salt: synthesis and structure10 marks
- 5(e)(i)Lanthanide contraction5 marks
- 5(e)(ii)Why Hf is placed below Zr5 marks
Question 6 50 marks
Question 7 50 marks