JEE Main202430 Jan 2024Evening ShiftChemistryd and f Block ElementsActual
The orange colour of K 2 Cr 2 O 7 and purple colour of KMnO 4 is due to
Options
- ACharge transfer transition in both.
- Bd → d transition in KMnO 4 and charge transfer transitions in K 2 Cr 2 O 7 .
- Cd → d transition in K 2 Cr 2 O 7 and charge transfer transitions in KMnO 4 .
- Dd → d transition in both.
Correct answer
A. Charge transfer transition in both.
Step-by-step solution
The deep blue colour of the solution K 2 Cr 2 O 7 is because an electron from the Oxygen lone pair is transferred to low lying Chromate ion orbital. Oxidation number of Chromium in Cr 2 O 7 2 - ⇒ 2 x + 7 × - 2 x = + 6 . The electronic configuration of Chromium is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 1 3 d 5 so it will lose six electrons to form Cr + 6 . Electronic configuration of Cr 6 + = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 since there are no electrons present in the d-orbital, the d-d transition will not occur. The oxygen