The green colour produced in the borax bead test of a...

The green colour produced in the borax bead test of a chromium (III) salt is due to
(a) $\mathrm{Cr}_{2}\left(\mathrm{~B}_{4} \mathrm{O}_{7}\right)_{3}$
(b) $\mathrm{Cr}_{2} \mathrm{O}_{3}$
(c) $\mathrm{Cr}\left(\mathrm{BO}_{2}\right)_{3}$
(d) $\mathrm{CrB}$

Key Concepts

Characteristic Colour Reactions

Characteristic colour reactions involve the development of distinct and identifiable colors when metal ions react with specific reagents. These color changes are significant diagnostic tools in qualitative analysis as they indicate the formation of particular chemical complexes, thereby aiding in the identification of the metal ion present.

Coordination Compounds

Coordination compounds are complexes formed when central metal ions bind to surrounding molecules or ions (ligands). The formation of these compounds, particularly with ligands like borate in the borax bead test, leads to specific electronic transitions that result in the appearance of unique colors, playing a crucial role in analytical identification procedures.

Borax Bead Test

The borax bead test is a qualitative analytical procedure used in inorganic chemistry to identify metal ions based on the specific colors they produce when incorporated into a borax (sodium borate) bead that has been heated. The test helps in differentiating metal ions by the unique complexes formed with borate, which emit characteristic colors upon flame heating.

Inorganic Qualitative Analysis

Inorganic qualitative analysis is a systematic approach to identify the constituents of a sample by employing various chemical tests that generate observable changes such as color, precipitate formation, or gas evolution. It relies on the unique reactivity of different metal ions with reagents, facilitating their identification based on characteristic reactions.

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