Constants I Periodic Table Part A Free-energy change, ?Go, is related to cell po

Question

Constants I Periodic Table Part A Free-energy change, ?Go, is related to cell potential, E°, by the equation AG nFE° where n is the number of moles of electrons transferred and F 96,500 C/(mol e) is the Faraday constant. When E is measured in voits, AG must be in joules since 1 J 1 C . V. Calculate the standard free-energy change at 25 °C for the following reaction: Mg(s) + Fe2 (a)Mg2(aq) + Fe(s) Express your answer to three significant figures and include the appropriate units. View Available Hint(s) Subrnit - Part B Calculate the standard cell potential at 25 C for the reaction x(s) + 2Y+(m)?X2+ (aq) + 2Y(s) where AH --703 k3 and AS 393 J/K Express your answer to three significant figures and include the appropriate units. View Available Hint(s) E Value Units Submit Next > Provide Feedback

Explanation / Answer

A)

For: the ave reactions

Fe2+ + 2 e? ? Fe(s) ?0.44

Mg2+ + 2 e? ? Mg(s) ?2.372

E°cell = Ered - Eox

=-0.44 - -2.372

= 1.932V

so

dG° = -nF*E°cell = -2*96500*1.932

= -372876J/mol

dG° = -372.87 kJ/mol

B)

Find dG°

dG° = dH - T*dS = -703*10^3 - 298*-393= -585886 J/mol

so..

dG° = -nF*E°cell

E°cell = dG°/(n*F) = 585886 /(2*96500 )

E°cell = 3.035678 V

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