Question

Name the gas which turns acidified potassium dichromate paper to green.

Answer 1

1. Acidified potassium dichromate (K₂Cr₂O₇) has an orange color.
2. The orange color will turn green when it reacts with Sulphur dioxide($\mathit{S}{\mathit{O}}_{\mathbf{2}}$).
3. The reaction will result in the formation of Potassium sulphate (K2SO4) and Chromium sulphate (Cr₂(SO₄)₃).
4. The formation of Chromium sulfate(${\mathit{K}}_{\mathbf{2}}\mathit{S}{\mathit{O}}_{\mathbf{4}}$) is the reason for the green color.
5. The reaction is,$\underset{AcidifiedPotassiumdichromate}{K_{2}C{r}_2{O}_7+H_{2}S{O}_4}+3S{O}_2\to \underset{Potassiumsulphate}{K_2\left(S{O}_4\right)}+H_{2}O+C{r}_2{\left(S{O}_4\right)}_3$
6. So, the gas is Sulfur dioxide.