UPSC Combined Geo-Scientist, Mains · 2026 · Mains Paper I
Q5(a). Colours of TcO₄⁻, MnO₄⁻ and MnO₄²⁻
Question
Suggest why the pertechnetate ion is red, permanganate ion is purple and manganate ion is green. Describe the most likely absorption that gives rise to colours in these ions. Also include energy level sketch showing how d-orbitals on metals interact with oxide orbitals to form molecular orbitals.
Model answer
The free solution for 2026 answers the questions picked in its time plan. Question 5 is answered in full in the Book Edition of the 2026 solutions of Geo-Scientist Chemistry Paper I.
Coverscharge-transfer spectraColours of TcO₄⁻MnO₄⁻ and MnO₄²⁻
All parts of Question 5
- 5(a) Colours of TcO₄⁻, MnO₄⁻ and MnO₄²⁻10 marks
- 5(b) Gravimetric estimation of nickel (g L⁻¹)10 marks
- 5(c) E^° of MnO₄⁻/Mn²⁺ by potentiometric titration10 marks