Question

The standard reduction potential data at 25C is given below.

E (Fe3+ .Fe2+) = + 0.77 V ;

E (Fe2+ .Fe) = - 0.44 V ;

E (Cu2+ .Cu) = + 0.34 V ;

E (Cu + .Cu) = + 0.52 V ;

E (O2(g) + 4H+ + 4e- → 2H2O) = + 1.23 V ;

E (O2(g) + 2H2O + 4e- → 4OH-) = + 0.40 V

E (Cr3+ .Cr) = - 0.74 V ;

E (Cr2+ .Cr) = -0.91 V

Which of the following statements is/are correct on the basis of above data :

(A) O2 is a better oxidising agent in acidic medium.

(B) Cr2+ show disproportionation to Cr and Cr3+ in water.

(C) O2 oxidises Fe2+ to Fe3+ in acidic medium.

(D) Cu + oxidises Fe to Fe2+ and H2O to O2 in acidic medium.

Answer 1

Correct option (A)(C)

Explanation:

As this is negative,

So reaction is non spontaneous.

(C) As SRP of O2 in acidic medium is more than SRP of Fe3+

So, O2 oxidises Fe2+ to Fe 3+ .

(D) As SRP of Cu+ /Cu is more than

SRP of Fe2+ /Fe, Cu+ oxidises Fe.

But SRP of Cu + /Cu is less than SRP of O2 /H2O in acidic medium.

So Cu+ do not oxidise H2O to O2 in acidic medium. This does not take place.