Question

The incorrect statement among the following is :

• A. VOSO₄ is a reducing agent
• B. RuO₄ is an oxidizing agent
• C. Cr₂O₃ is an amphoteric oxide
• D. Red colour of ruby is due to the presence of Co³⁺

Hint:

Ruby ($Al_2O_3$ with $Cr^{3+}$) and Emerald ($Be_3Al_2Si_6O_{18}$ with $Cr^{3+}$) both owe their colors to $Cr^{3+}$ impurities, but the different crystal fields result in different colors.

Answer 1

The Correct Option is D

Step 1: $V$ in $VOSO_4$ is in +4 state. It can be oxidized to +5, so it acts as a reducing agent. (Correct)
Step 2: $Ru$ in $RuO_4$ is in its highest oxidation state (+8), making it a powerful oxidizing agent. (Correct)
Step 3: $Cr_2O_3$ is a well-known amphoteric oxide of Chromium. (Correct)
Step 4: The red colour of ruby is actually due to the presence of $Cr^{3+}$ ions as impurities in the $Al_2O_3$ lattice, not $Co^{3+}$. Statement (D) is incorrect.