This question tests your knowledge of the characteristic colors of specific inorganic compounds, particularly precipitates and complex ions formed in qualitative analysis. Many compounds have distinct colors that help in their identification.

Let's analyze each option:

Option 1: BaCrO₄ (Barium Chromate) is a well-known yellow precipitate. It is formed when barium ions react with chromate ions.

Option 2: (NH₄)₃[As(Mo₃O₁₀)₄] is the formula for ammonium arsenomolybdate. It is a yellow precipitate, famously used as a test for arsenate and phosphate ions.

Option 3: K₃[Co(NO₂)₆] is potassium hexanitritocobaltate(III). This compound is a yellow precipitate and is used in the qualitative analysis of potassium ions.

Option 4: Zn₂[Fe(CN)₆] is zinc ferrocyanide. Unlike the others, this compound is not yellow. It typically forms a bluish-white or pale gray precipitate. This reaction is used as a confirmatory test for zinc ions.

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

Related Topics & Formulae

Qualitative Analysis: This is a branch of chemistry that deals with the identification of elements or grouping of elements present in a sample. The color of a precipitate is a key physical property used in this identification process.

Complex Ions: Many of these colored compounds are coordination complexes, where a central metal ion is surrounded by ligands. The color often arises from the absorption of certain wavelengths of light due to d-d electron transitions (in transition metals) or charge transfer.

Common Colored Precipitates:

• Yellow: BaCrO₄, PbCrO₄, CdS, (NH₄)₃PO₄·12MoO₃, K₃[Co(NO₂)₆]
• Black: HgS, CuS, PbS, MnO₂
• White: BaSO₄, PbCl₂, AgCl (initially)

Memorizing these common colors is essential for solving such problems.