Q. 33

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

(i) Cu + Zn2+ Cu2+ + Zn

(ii) Mg + Fe2+ Mg2+ + Fe

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

(iv) Fe + Cd2+ Cd + Fe2+

Answer :

The electrochemical series gives a relative strength arrangement of standard electrode reduction potentials of common ions and elements. It is arranged in increasing order of Reduction Potential from bottom to top with F being at the top and Li being at the bottom.

Now whether a reaction should takes place or not would depend on the net cell EMF of the cell, given by equation

Option (i)Cu + Zn2+ Cu2+ + Zn

Here Cu undergoes oxidation so it acts as anode and Zn acts as cathode. So from the table

For cathode E°cathode = -0.76 V

For anode E°anode = 0.52 V

As the EMF of cell is negative the given reaction will not occur spontaneously if they were to form a cell placed as electrodes.

Option (ii) Mg + Fe2+ Mg2+ + Fe

Similarly, we can say that Mg undergoes oxidation and Fe undergoes reduction.

cathode = -0.44 V

anode = -2.36 V

Positive EMF implies that the reaction will give out energy and attain stability, thus it will occur spontaneously. So the given redox reaction will occur.

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

Here Br undergoes reduction thus acting as cathode and Cl acting as anode.

For cathode E°cathode = 1.09 V

For anode E°anode = 1.36 V

The negative potential prevents easy reaction, so the redox reaction will not occur.

Option (iv) Fe + Cd2+ Cd + Fe2+

Fe is the cathode and Cd is the anode

For cathode E°cathode = -0.44 V

For anode E°anode = -0.40 V

The negative potential prevents easy reaction, so the redox reaction will not occur.

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Balancing of Redox Reactions70 mins
Interactive Quiz - Balancing of Redox ReactionsFREE Class
Interactive Quiz on balancing of redox reactions47 mins
Learn how to balance Redox ReactionsFREE Class
Redox Titrations40 mins
Interactive quiz on Oxidation,reduction, Oxidising agent, Reducing agent42 mins
Oxidation, Reduction, Oxidising agent, Reducing Agent41 mins
Interactive quiz on Oxidation number - 0242 mins
Oxidation number55 mins
Interactive Quiz on Redox reaction | Check YourselfFREE Class
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses