UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper II covers physical chemistry.
Kinetic theory and the gaseous state: every question, 2016 to 2025
43 parts worth 289 marks have been set on this unit in UPSC Geo-Scientist Chemistry Mains Paper II from 2016 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
Real gases, deviation of gases from ideal behaviour; compressibility factor; van der Waals equation of state and its characteristic features. Existence of critical state. Critical constants in terms of van der Waals constants. Law of corresponding states and significance of second virial coefficient. Boyle temperature.
Notes: Kinetic theory of gases: Maxwell distribution, collisions, mean free path, effusion and transport (full notes) · short notes
Notes: Real gases: van der Waals equation, critical constants, Boyle temperature (full notes) · short notes
2025
- Q1(a) Why Z > 1 for H₂ and He at all pressures5 marks Answered
- Q1(b) Corresponding state of H₂S for N₂ at 25 °C and 1 atm5 marks Answered
- Q2 Compressibility factor and molar volume of a real gas10 marks Answered
2024
- Q1(a) Volume and critical temperature of two van der Waals gases5 marks Answered
- Q1(b) Second virial coefficient A₂ and the Boyle temperature5 marks Answered
- Q2 Boyle temperature of a van der Waals gas10 marks Answered
- Q12(a) Gas left in an evacuated flask; pressure after adding N₂10 marks Question only
2023
- Q1(a) van der Waals equation: meaning of a and b5 marks Answered
- Q1(b) Exceptional behaviour of hydrogen and helium5 marks Answered
- Q2 Critical constants of a van der Waals gas and Zc10 marks Answered
2022
- Q1(a) Postulates of kinetic theory and the two that fail5 marks Answered
- Q1(b) Boyle temperature of oxygen as a van der Waals gas5 marks Answered
- Q2(a) Reduced equation of state from the van der Waals equation5 marks Answered
- Q2(b) Excluded volume is four times the molecular volume5 marks Answered
- Q14(b) Pressure of CO₂ from the reduced van der Waals equation10 marks Question only
2021
- Q1(a) Conditions for ideal behaviour of real gases5 marks Answered
- Q1(b) Compressibility factor and Z against P plots5 marks Answered
- Q2 Virial equation; B from the van der Waals equation10 marks Answered
- Q10(b) Molecular diameter of helium from the van der Waals b5 marks Answered
- Q11(a) Boyle temperature and its meaning for H₂, He, N₂ and NH₃10 marks Question only
2020
- Q1(a) Critical-point inflection5 marks Answered
- Q1(b) Boyle and inversion temperatures5 marks Answered
- Q2 Comparing van der Waals gases10 marks Answered
- Q11(a) Virial expansion and Boyle temperature10 marks Answered
2019
- Q1(a) Atomicity from heat capacities5 marks Answered
- Q1(b) Units of attraction parameter5 marks Answered
- Q2(a) Normalisation of the Maxwell distribution5 marks Answered
- Q4 Compressibility factor10 marks Answered
- Q11(a) Equilibration of molecular kinetic energies10 marks Answered
2018
- Q1(a) Equal molecular speeds5 marks Answered
- Q1(b) Fugacity under repulsion5 marks Answered
- Q1(e) Joule–Thomson cooling5 marks Answered
- Q2(a) Logarithmic ideal-gas plot5 marks Answered
- Q2(b) Boyle temperature of helium5 marks Answered
- Q13(a) Thermal energy of oxygen10 marks Answered
- Q13(b) Reduced van der Waals equation10 marks Answered
2017
- Q1(a) Van der Waals equation8 marks Answered
- Q7(a) Most probable speed from the Maxwell distribution8 marks Question only
- Q15(a) Van der Waals critical constants8 marks Answered
2016
- Q1(a) Virial equation5 marks Answered
- Q1(d) Equipartition in hydrogen5 marks Answered
- Q2(ii) Effusion of a mixture5 marks Answered
- Q2(i) Effusion of ammonia5 marks Answered
UPSC Combined Geo-Scientist (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All fifteen questions of each paper, with the question printed above its answer
- Numericals worked from formula to result with units; graphs with labelled axes
- Topic-wise weightage and a topic-wise index