05-10-2018, 05:17 PM

Fe3+ + Y-4 ::equil:: FeY- Kf=1.3X1025

Fe2+ + Y+4 ::equil:: FeY2- Kf=2.1x1014

Calculate the E° for the process

FeY- + e- ::equil:: FeY2-

The answer is said to be 0.13 V.

My attempt since, the half reaction for the following is

Fe3+ + e- :rarrow: Fe2+ E°= +0.77 V

Fe2+ + e- :rarrow: Fe(s) E°= - 0.44 V

E1 = 0.77- (RT/Fn)ln 1/Kf

E1 = 0.77 - 0.0257/(3)(ln 1/ 1.3X1025) I put three here cuz there's 3 electrons to form Fe(s)

E1 = 1.27 V

E2 = -0.44- (RT/Fn)ln 1/Kf

E2 =-0.44- 0.0257/(2)(ln 1/2.1x1014) put three here cuz there's 2 electrons to form Fe(s)

E2 = -0.0162 V

If add or substract this answers I will still not get 0.13 V please help me DO I still have to use Nert's Equation ?

Fe2+ + Y+4 ::equil:: FeY2- Kf=2.1x1014

Calculate the E° for the process

FeY- + e- ::equil:: FeY2-

The answer is said to be 0.13 V.

My attempt since, the half reaction for the following is

Fe3+ + e- :rarrow: Fe2+ E°= +0.77 V

Fe2+ + e- :rarrow: Fe(s) E°= - 0.44 V

E1 = 0.77- (RT/Fn)ln 1/Kf

E1 = 0.77 - 0.0257/(3)(ln 1/ 1.3X1025) I put three here cuz there's 3 electrons to form Fe(s)

E1 = 1.27 V

E2 = -0.44- (RT/Fn)ln 1/Kf

E2 =-0.44- 0.0257/(2)(ln 1/2.1x1014) put three here cuz there's 2 electrons to form Fe(s)

E2 = -0.0162 V

If add or substract this answers I will still not get 0.13 V please help me DO I still have to use Nert's Equation ?