Question

The residual energy of a cold-worked steel as determined calorimetrically is 21 J/g. Calculate the increased tendency in volts for iron to corrode when cold worked. (Assume that the entropy change is negligible.)

Answer 1

ANSWER : ince corrosion of iron is a spontaneous process, in a spontaneous process work done is given by

Workdone = charge transfered x potential difference

Work done = nFE⁰ --------- eq( I)  [ where n= number of electrons involved, in this system n=1(ferrous to ferric state),

                                           F= Farady = 96500C , E⁰ = standard emf in volts.]

Since corrosion of iron is a spontaneous process maximum work done = - G⁰ ------------- eq (2)

From eq (1) and eq (2) - G⁰ = nFE⁰ ==> E⁰ = -G⁰ / n x F

                                         E⁰ = - (21) / 1 x 96500C = -0.000218 volts [G⁰ = 21 J/g from given data ]

        therefore emf in volts = -0.000218 volts.