Q3(d). Cubic diffraction selection rules
Metal A gives powder XRD lines from (110), (200), (220), (311), (400), (331), while B gives (110), (200), (211), (220), (301), (222). Comment on the space lattices and justify. What fraction of A's unit-cell space is available for the tightest possible packing?
Model answer
The free solution for 2024 answers questions 1, 2, 4, 5 and 8, the ones picked in its time plan. Question 3 is answered in full in the IFoS Chemistry Paper I, 2021 to 2025 book, with every part of every paper.
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UPSC Indian Forest Service (Main) Chemistry Paper I: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Physical chemistry numericals worked with units; inorganic structures drawn
- Topic-wise weightage and a topic-wise index
Coverspowder X-ray diffractionsystematic absencesfcc and bcc latticesMiller indicespacking fraction
All parts of Question 3
- 3(a) Thermodynamic transition-state theory15 marks
- 3(b) Heat capacity of an Einstein crystal10 marks
- 3(c) Photostationary dimer concentration10 marks
- 3(d) Cubic diffraction selection rules5 marks