Question

When SO2 gas is passed through saturated solution of hydrogen sulphide, the following reaction occurs: SO2+ H2S=2H20+3S

Answer 1

see it is very simple. first you need to see which substance has hydrogen before reaction and which one has later. thus H2S has hydrogen. Now see which product has hydrogen, i.e. H2O. now see where does O belong from. O belongs from SO2. thus SO2 is reduced to H2O and H2S is oxidised to H2O. always remember that oxidisation is reverse of reduction.

hope this helps you!! :)