VKC ScienceChemistry for written exams Telegram

UPSC Combined Geo-Scientist

Chemist

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

Mains Paper II covers physical chemistry.

UPSC Combined Geo-Scientist, Mains · 2021 · Mains Paper II

Q3. Lattice type from first-order Bragg reflections

Question

The first order reflections from the 100, 110 and 111 planes of a given cubic crystal were found to occur at angles 5.9°, 8.4° and 5.2° respectively. Determine the type of crystal lattice to which the crystal belongs.

Answer in brief

d₁₀₀ : d₁₁₀ : d₁₁₁ = 1 : 0.704 : 1.134 ≈ 1 : 1/√2 : 2/√3 ⇒ face-centred cubic lattice.

Part of VKC Basic

Read the key points and the full model answer with VKC Basic

VKC Basic (₹999 for 6 months) opens every solved answer, the notes, the handbook and the daily answer archive. Every Mains test series includes it.

See what is included Already a member? Sign in

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.

The handwritten model answer pages open with the VKC plan.
Read the whole 2021 solution2021 question paper

Topic notes: crystal systems, Bragg's law, X-ray diffraction and radius ratio, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversBragg's lawX-ray diffractioncubic latticeface-centred cubicsystematic absencesinterplanar spacing