Question

When sulphur dioxide gas is passed through acidified potassium dichromate solution, the colour of the solution changes from :
(1) orange to yellow
(2) orange to green
(3) green to orange
(4) yellow to green

Answer 1

When sulphur reacts with orange coloured acidified potassium dichromate solution, it changes the orange coluored solution to green due to the formation of green coloured chromium sulphate.

${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+{\mathrm{SO}}_2\stackrel{{\mathrm{H}}^{+}}{\to }{\mathrm{Cr}}_2({\mathrm{SO}}_4{)}_3+{\mathrm{K}}_2{\mathrm{SO}}_4+{\mathrm{H}}_2\mathrm{O}$

Hence the correct option is 2.