Question

A. Which transformation could take place at the anode of an electrochemical cell?

a. O₂ --> H₂O

b. H₂AsO₄ ---> H₃AsO₃

c. NO --> NO₃^-

d. VO₂⁺ ---> VO²⁺

B Which of the following could spontaneously reduce Fe²⁺ (aq) to iron metal?

Pb²⁺ (aq), Al³⁺ (aq), Pb(s), Al(s)

and why?

Answer 1

A ) Always oxidation takes place at anode.So the oxidation state of the elements will increases.

0 -2

a. O₂ --> H₂O ----> decrease in oxidation state .Which does not takes place at anode

+6 +3

b. H₂AsO₄ ---> H₃AsO₃   ----> decrease in oxidation state .Which does not takes place at anode

+2 +5

c. NO --> NO₃^- ----> increase in oxidation state .Which takes place at anode

d. VO2+ ---> VO2+

No change in oxidation states so it will not takes place either at anode or at cathode.

B) In electrochemical series lower reduction potential metal can reduces higher reduction potential metal

The reduction potential values are as follows :

E _{Pb2+/ Pb} = -0.13 V

E _{Al3+/ Al} = -1.66 V

E _{Fe2+/ Fe} = -0.44 V

So Pb wil, easily reduces Fe2+ ions