UPSC Combined Geo-Scientist, Mains · 2026 · Mains Paper III
Q2(a). Identify the metal from three XRD peaks
Question
The first three peaks in an X-ray diffractogram (XRD) of metal M are obtained at 2θ values of 38.6°, 55.7° and 70.0°, using Cu Kα radiation (λ=1.542 Å). Compare the crystal structure and atomic radii with those given in the table below, and identify M: Al (FCC, 1.431), Au (FCC, 1.442), Pt (FCC, 1.387), Cr (BCC, 1.249), Mo (BCC, 1.363), Ta (BCC, 1.429), Ti (HCP, 1.445), Zn (HCP, 1.332), Cd (HCP, 1.490) (radius in Å).
Model answer
The free solution for 2026 answers the questions picked in its time plan. Question 2 is answered in full in the Book Edition of the 2026 solutions of Geo-Scientist Chemistry Paper III.
Coversindexing of a powder patternIdentify the metal from three XRD peaks
All parts of Question 2
- 2(a) Identify the metal from three XRD peaks15 marks
- 2(b) Spectrophotometric determination of Fe²⁺ with 1,10-phenanthroline10 marks
- 2(c) Dating a geological deposit by ICP-MS5 marks