Question

$\textbf{The orange colour of } \text{K}_2\text{Cr}_2\text{O}_7 \textbf{ and purple colour of KMnO}_4 \textbf{ is due to}$

• A. d$\rightarrow$d transition in K$_2$Cr$_2$O$_7$ and charge transfer transitions in KMnO$_4$.
• B. d$\rightarrow$d transition in KMnO$_4$ and charge transfer transitions in K$_2$Cr$_2$O$_7$.
• C. Charge transfer transition in both.
• D. d$\rightarrow$d transition in both.

Answer 1

The Correct Option is C

The colors observed in \(K_2Cr_2O_7\) and \(KMnO_4\) arise from electronic transitions within the compounds:

Charge Transfer Transitions: Charge transfer transitions involve the movement of an electron from a filled orbital (usually a ligand) to an empty orbital of a metal ion.

In the case of \(K_2Cr_2O_7\), the orange color is primarily due to the charge transfer transition associated with the \(Cr^{6+}\) ion.

In \(KMnO_4\), the purple color results from a similar charge transfer transition involving the \(Mn^{7+}\) ion.

Summary of Transitions: Both compounds exhibit charge transfer transitions rather than d → d transitions, which are more common in transition metal complexes with partially filled d orbitals.

Thus, the correct explanation for the observed colors in both \(K_2Cr_2O_7\) and \(KMnO_4\) is: Charge transfer transition in both.