Q32 of 37 Page 110

Explain redox reactions on the basis of electron transfer. Give suitable examples.

Initially it was thought that the oxidation & reduction are just related to addition of oxygen molecule and removal of hydrogen atoms. As the process developed study showed that, its mostly related to transfer of electrons from one species to another resulting in more stable ions.

Thus in a redox reaction if one species loses electrons its considered to be undergoing oxidation reaction and acts as oxidizing agent or oxidant, and for species who accepts electrons is said to undergo reduction and behave as reductant.


This transfer is mainly based on the relative electronegativity of difference between the two interacting species. The more electronegative element attracts electrons and the electropositive element loses electrons.


For example, consider a redox reaction between Zn and HCl



Here the zinc loses electrons to a more electronegative atom Cl with the reaction for oxidation and reduction as follows:


Oxidation:


Reduction:


Thus transfer of electrons causes the redox reaction to occur.


More from this chapter

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30

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

Assertion (A): The decomposition of hydrogen peroxide to form water and oxygen is an example of disproportionation reaction.


Reason (R) : The oxygen of peroxide is in –1 oxidation state and it is converted to zero oxidation state in O2 and –2 oxidation state in H2O.


(i) Both A and R are true and R is the correct explanation of A.


(ii) Both A and R are true but R is not the correct explanation of A.


(iii) A is true but R is false.


(iv) Both A and R are false.


31

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

Assertion (A) : Redox couple is the combination of oxidised and reduced form of a substance involved in an oxidation or reduction half cell.


Reason (R) : In the representation E° Fe3+/fe2+and E°cu2+/cu , Fe3+ / Fe2+ and Cu2+ are redox couples.


(i) Both A and R are true and R is the correct explanation of A.


(ii) Both A and R are true but R is not the correct explanation of A.


(iii) A is true but R is false.


(iv) Both A and R are false


33

On the basis of standard electrode potential values, suggest which of the following reactions would take place? (Consult the book for Edegree value).

(i) Cu + Zn2+ Cu2+ + Zn


(ii) Mg + Fe2+ Mg2+ + Fe


(iii) Br2 + 2Cl- Cl2 + 2Br-


(iv) Fe + Cd2+ Cd + Fe2+


34

Why does fluorine not show disproportionation reaction?