which of the followoing reactions are oxidation-reduction reactions?

Question

4(NH3) + 5(O2 )-----> 4NO + 6(H2O)
2NO + O2 -------> 2NO2
3(NO2) + H2O -----> 2(HNO3) + NO

how can i identify the oxidizing and reducing agent in each redox reaction?

Answer 1

They all are !

Give each element in the reaction an oxidation number, then see which ones change. An increase in oxidation number is a loss of electrons (oxidation), while a decrease in oxidation number is a gain of electrons (reduction).

An oxidising agent causes another substance to be oxidised; it takes electrons from the other substance, and is therefore, itself, reduced.

For the first reaction.

reactants
NH3 : N = -3, H = +1
O2 : O = 0
products
NO2 : N = +4, O = -2
H2O : H = +1, O = -2

nitrogen has lost electrons; it has been oxidised; it is a reducing agent

oxygen has gained electrons; it has been reduced; it is an oxidising agent

hydrogen has been neither oxidised nor reduced