UPSC Combined Geo-Scientist, Mains · 2016 · Mains Paper II
Q1(j). Monolayer surface area
Question
130 mL of N₂, corrected to 0° C and 1 bar, forms a monolayer on a solid. Calculate its surface area if the cross-sectional area per molecule is 16.2 Ų.
Answer in brief
The surface area is 5.58×10² m².
Key points
- At the stated pressure, n=PV/(RT)=(10⁵)(130×10⁻⁶)/(8.314×273.15)=5.724×10⁻³ mol.
- The molecular area is 16.2×10⁻²⁰ m², and the number of adsorbed molecules is nNA.
- Thus A=nNAa=558.45 m². This is total surface area, not specific area per gram.
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.
CoversMonolayer surface areaAdsorption
All parts of Question 1
- 1(a) Virial equation5 marks
- 1(b) Inclined capillary5 marks
- 1(c) Entropy and diffraction5 marks
- 1(d) Equipartition in hydrogen5 marks
- 1(e) Expansion cooling of helium5 marks
- 1(f) Temperature dependence of equilibrium5 marks
- 1(g) Ammonium chloride pH5 marks
- 1(h) Reverse osmosis5 marks
- 1(i) Rate-law determination5 marks
- 1(j) Monolayer surface area5 marks
- 1(k) Electrolysis of copper sulfate5 marks
- 1(l) Ionization of helium ion5 marks
- 1(m) Photochemical quantum yield5 marks
- 1(n) Momentum in a box5 marks
- 1(o) Formaldehyde electronic transitions5 marks
- 1(p) NMR distinction of ethers5 marks