Answer to Question #162043 in Physical Chemistry for Eden

Question

Calculate the standard free energy changes for the following reactions at 25°C using the data table

below and using the equation :

ΔG°(rxn) = Ʃ ΔG°f (products) - Ʃ ΔG°f (rectants )

Substance ΔG° f (kJ/mol) S°(J/K·mol

CH 4 (g) -50.8 186.264

CO 2 (g) -394.4 213.74

H 2 O (l) -237.2 109.6

MgO (s) -569.6 26.94

a. CH 4 (g)+ 2 O 2 (g) -> CO 2 (g)+ 2 H 2 O (l)

b. 2MgO(s)-> 2Mg (s) + O 2

Answer 1

a) using formula,

ΔG°(rxn) = Ʃ ΔG°f (products) - Ʃ ΔG°f (rectants)

= (2×(--237.2) + (-394.4)) - (-50.8)

= [-818] kJ/mol

b) using above formula,

ΔG°(rxn) = Ʃ ΔG°f (products) - Ʃ ΔG°f (rectants)

= (0+0)-(2×(-569.6))

= [-1139] kJ/mol