Question

Discuss each conclusion below from a study of redox reactions:

a) The sulfide ion functions only as a reducing agent

b) The sulfate ion functions only as an oxidizing agent

c) Sulfur dioxide functions as either an oxidizing agent or a reducing agent

Answer 1

a)

if sulfide ion act as reducing agent it losses electrons .

S^-2 + Cl2 -----------------------> S + 2Cl-

Suphur oxidation state changes from -2 to 0 . it is oxidation reaction . so S^-2 can act as a reducing agent

Cl2 act as a oxidising agent here Cl oxidation state changes from 0 to   - 1. it is reduction . so Cl2 is a oxidising agent

b)

SO4^-2 + 4H+ + 2e-   ------------------------> H2SO3 + H2O

sulfur oxidation in SO4^-2 is +6   and in products +4 oxidation state .

S ( +6----------> +4 ) it is reduction reaction. so SO4^-2 can act as a oxidising agent

c)

MnO4^- + SO2 ------------------> Mn^2+ + SO4^2-

               (+4)                                             (+6)

S oxidation state changes from +4 to +6 . it is oxidation reaction . SO2 can act as a reducing agent

SO2 + 2H2S --------------------------> 3S + 2 H2O

(+4)                                                    (0)

sulphur oxidation state changes from +4 to 0 . it is reduction. so SO2 can act as oxidising agent