UPSC Combined Geo-Scientist, Mains · 2024 · Mains Paper I
Q1(a). Minerals and their compositions
Question
Match the following: (i) Dolomite (ii) Corundum (iii) Sphalerite (iv) Silicon (v) Chalcopyrite with 1. Alumina 2. MgCO₃·CaCO₃ 3. CuFeS₂ 4. ZnS 5. Semiconductor.
Answer in brief
(i) – 2; (ii) – 1; (iii) – 4; (iv) – 5; (v) – 3.
Key points
- Dolomite: CaMg(CO₃)₂, conventionally written MgCO₃·CaCO₃; a double carbonate.
- Corundum: crystalline α-Al₂O₃, or alumina.
- Sphalerite: the cubic zinc-blende form of ZnS.
- Silicon: a covalent-network semiconductor; its conductivity can be controlled by doping.
- Chalcopyrite: CuFeS₂, an important copper-bearing sulfide mineral.
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.
Coversdolomitecorundumsphaleritechalcopyriteminerals compositionsemiconductor
All parts of Question 1
- 1(a) Minerals and their compositions5 marks
- 1(b) Magnetic moment of titanium(III)5 marks
- 1(c) Choosing indicators5 marks
- 1(d) Silica by volatilisation gravimetry5 marks
- 1(e) Spontaneity of Fe²⁺ oxidation5 marks
- 1(f) Oxidising power and charge transfer5 marks
- 1(g) pH dependence of cyanide masking5 marks
- 1(h) Terminal and bridging carbonyl bands5 marks
- 1(i) Identifying radioactive decay5 marks
- 1(j) Why ordinary lanthanoid carbonyls are unstable5 marks