Question

Which of the following compounds is not coloured yellow?

Options

• Zn₂[Fe(CN)₆]

• K₃[Co(NO₂)₆]

• (NH₄)₃[As(Mo₃O₁₀)₄]

• BaCrO₄

Answer 1

Zn₂[Fe(CN)₆]

Explanation:

• Zn₂[Fe(CN)₆] is colorless because Zn²⁺ has a d¹⁰ configuration, which does not absorb visible light.
• K₃[Co(NO₂)₆] and BaCrO₄ are both yellow due to the presence of Co³⁺ and Cr⁶⁺, which absorb light in the visible range.
• (NH₄)₃[As(Mo₃O₁₀)₄] is colorless or white, not yellow.

Thus, Zn₂[Fe(CN)₆] is the compound that is not yellow.