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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2016 · Mains Paper III

Q1(d). Density of silver

Question

Silver has a ccp lattice with a=408.6 pm and atomic mass 107.9. Calculate its density.

Answer in brief

ρ=10.51 g cm⁻³.

Key points

  • A ccp/fcc unit cell contains Z=8/8+6/2=4 atoms. Convert a=4.086×10⁻⁸ cm.
  • ρ=ZM/(NAa³)=4(107.9)/[6.02214×10²³(4.086×10⁻⁸)³]=10.506 g cm⁻³.

The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

Model answer to Q1(d), 2016 Mains Paper III: solution pages 1 and 2
Solution pages 1 and 2 of 22
Read the whole 2016 solution2016 question paper

CoversDensity of silverCrystallography

All parts of Question 1