Question

Which gas is greenish-yellow in colour?

Answer 1

Chlorine gas (Cl₂) is greenish-yellow in colour. This colour helps in its qualitative analysis. It has a sharp choking odour.

• The analysis which aims at detecting the presence of any substance in a given sample is called qualitative analysis.

The evolution of Chlorine gas takes place as follows: Manganese dioxide (MnO₂) when heated with concentrated Hydrochloric acid (HCl) to produce Chlorine gas (Cl₂) along with Manganese chloride (MnCl₂) and water (H₂O).

$$\begin{gathered} {\mathrm{MnO}}_2\left(\mathrm{s}\right)+4\mathrm{HCl}\left(\mathrm{l}\right)\stackrel{∆}{\to }{\mathrm{MnCl}}_2\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right) \\ (\mathrm{Manganese}\mathrm{dioxide})(\mathrm{Hydrochloric}\mathrm{acid})(\mathrm{Manganese}\mathrm{chloride})\left(\mathrm{Water}\right)\left(\mathrm{Chlorine}\right) \end{gathered}$$

The chlorine gas liberated here is greenish-yellow in colour.