SO2+ 1/2O2 = SO3
0.4-0.2 before equilibrium.
Change x 0.5x x
Balance 0.4 x 0.2-0.5 x
(0.6-0.5x)/0.6 = 16/20
Find x
The conversion rate of SO2 is 100% x/0.4=?
You do the rest yourself.
4) I forgot the chemical reaction formula of electrochemistry, and it should be done directly according to that electrode reaction.