identify oxidizing and reducing agents in case of redox reactions. i. H3PO4(aq) + 3KOH(aq) → K3PO4(aq) + 3H2O(l)

Question

Using oxidation number concept, identify the redox reactions, identify oxidizing and reducing agents in case of redox reactions.

i. H₃PO_4(aq) + 3KOH_(aq) → K₃PO_4(aq)  + 3H₂O_(l)

ii. Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g)

iii. \(6Fe^{2+}_{(aq)}\) + \(BrO^-_{3(aq)}\) + \(6H^+_{(aq)}\) → \(6Fe^{3+}_{(aq)}\) + \(Br^-_{(aq)}\)+ 3H₂O_(l)

Answer 1

i. H₃PO_4(aq) + 3KOH_(aq) → K₃PO_4(aq)  + 3H₂O_(l)

a. Write oxidation number of all the atoms of reactants and products.

b. Since, the oxidation numbers of all the species remain same, this is NOT a redox reaction.

Result : 

The given reaction is NOT a redox reaction.

ii. Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g)

a. Write oxidation number of all the atoms of reactants and products.

b. Identify the species that undergoes change in oxidation number.

c. The oxidation number of Zn increases from 0 to +2 and that of H decreases from +1 to 0. Because oxidation number of one species increases and that of other decreases, the reaction is redox reaction. 

d. The oxidation number of Zn increases by loss of electrons and therefore, Zn is a reducing agent and itself is oxidized. On the other hand, the oxidation number of H decreases by gain of electrons and therefore, H is oxidising an agent and itself is reduced by gain of electrons.

Result :

1. The given reaction is a redox reaction. 

2. Oxidant/oxidising agent : HCl 

3. Reductant/reducing agent : Zn

iii. \(6Fe^{2+}_{(aq)}\) + \(BrO^-_{3(aq)}\) + \(6H^+_{(aq)}\) → \(6Fe^{3+}_{(aq)}\) + \(Br^-_{(aq)}\)+ 3H₂O_(l)

a. Write oxidation numbers of all the atoms of reactants and products.

b. Identity the species that undergoes change in oxidation number.

c. The oxidation number of Fe increases from +2 to +3 and that of Br decreases from +5 to -1. Because oxidation number of one species increases and that of the other decreases, the reaction is a redox reaction.

d. The oxidation number of Fe increases by loss of electrons and therefore, Fe is a reducing agent and itself is oxidized. On the other hand, the oxidation number of Br decreases by gain of electrons and therefore, Br is an oxidising an agent and itself is reduced.

Result :

1. The given reaction is a redox reaction.

2. Oxidant/oxidising agent : BrO₃^-

3. Reductant/reducing agent : Fe²⁺