Question

13. (a) Calculate AGº and log K, for the following reaction at 298 K:
2Cr(s) + 3Fe2+ (aq) →
2Cr3+ (aq) + 3Fe(s)
Given : E = 0.30 V
(b) Using the Eº values of A and B, predict which is better for coating
the surface of iron [E°(Fe2+|Fe) = -0.44 V] to prevent corrosion and
why?
Given: E°(A2+|A) = -2.37 V : E°(B2+|B) = -0.14 V
​

Answer 1

Answer:

Cr(s) → Cr

3+

(aq)+3e

−

]×2

Fe

2+

(aq)+2e

−

→ Fe(s) ]×3

________________________________________________

2Cr(s)+3Fe

2+

(aq)→2Cr

3+

(aq)+3Fe(s),n=6

________________________________________________

Here , n=6,E

cell

∘

=0.30V

Substituting the values in the expression , logK

c

=

0.059

n

E

cell

∘

, , we get

logK

c

=

0.059

6

×0.30 or logK

c

=30.5084

K

c

= Antilog (30.5084) or logK

c

=3.224×10

30

ΔG

∘

=−nFE

cell

∘

=−6×96500×0.30=−173700Jmol

−1

ΔG

∘

=−173.7kJmol

−1