Redox Reactions

(i) H2O2 act as oxidising agent as well as reducing agent depending on condition.
(ii) H2SO3 act as oxidising agent as well as reducing agent depending on condition.
(iii) HNO2 act as oxidising agent as well as reducing agent depending on condition.
(iv)H3PO4 can not act both as oxidising and reducing agent.
H3PO4 can act as only oxidising agent.
H3PO4⇌3H++PO43−