In sodium carbonare bead rest, chromium salrs (grcen) changc...

In sodium carbonare bead rest, chromium salrs (grcen) changc ro coloured bead
(a) Yellow, $\mathrm{Na}_{2} \mathrm{CrO}_{0}$
(b) Orangc, $\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$
(c) Yellow, $\mathrm{PbCrO}_{4}$
(d) Yellow, $\mathrm{BaCrO}_{4}$

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Key Concepts

Chromate and Dichromate Equilibrium

Chromate (CrO4^2–) and dichromate (Cr2O7^2–) ions are interconvertible species whose existence depends on the pH of the solution. Chromate typically imparts a yellow color while dichromate gives an orange color. Understanding this equilibrium and the related color changes is important in qualitative analysis, as the conditions of the test (such as an alkaline flame in the bead test) can favor one form over the other.

Sodium Carbonate Bead Test

This is a classic procedure in inorganic qualitative analysis where a heated bead of sodium carbonate is used to react with a sample. When certain metal ions (or in this case, chromium compounds) are present, the reaction with the sodium carbonate and subsequent heating leads to the formation of colored compounds on the bead. This color change is a key diagnostic feature used to identify the ion present.

Qualitative Analysis

This refers to the set of techniques used in analytical chemistry to identify the chemical constituents of a sample. In inorganic qualitative analysis, specific reactions are employed that produce color changes or precipitates when certain ions are present, thereby allowing the chemist to determine which ions are in the sample.

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