UPSC Combined Geo-Scientist, Mains · 2019 · Mains Paper II
Q1(o). Spectral wavelength shifts
Question
Explain bathochromic and hypsochromic shifts, giving an example of each.
Answer in brief
Bathochromic means a shift to longer wavelength (lower energy); hypsochromic means a shift to shorter wavelength (higher energy).
Key points
- Increasing conjugation usually narrows an electronic excitation gap.
- Hydrogen-bonding polar solvents can stabilise the oxygen lone-pair ground state of a carbonyl more than its n→π* excited state, increasing the gap and shifting this…
- These terms describe band position, not intensity. Hyperchromic and hypochromic changes instead describe increases and decreases in absorbance or molar absorptivity.
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.
CoversSpectral wavelength shiftsUV–visible spectroscopy
All parts of Question 1
- 1(a) Atomicity from heat capacities5 marks
- 1(b) Units of attraction parameter5 marks
- 1(c) Surface energy of cube and sphere5 marks
- 1(d) Atoms in a BCC sample5 marks
- 1(e) Volume independence of ideal-gas heat capacity5 marks
- 1(f) Entropy on doubling volume5 marks
- 1(g) Single-ion activity coefficients5 marks
- 1(h) Ammonia buffer5 marks
- 1(i) Pure-component vapour pressures5 marks
- 1(j) Zero-order half-life5 marks
- 1(k) Physical and chemical adsorption5 marks
- 1(l) Iron redox-electrode potential5 marks
- 1(m) Energy of one einstein5 marks
- 1(n) Bohr quantisation from matter waves5 marks
- 1(o) Spectral wavelength shifts5 marks
- 1(p) Bromobutane with one NMR signal5 marks