Solutions
- Page ID
- 11066
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Using the tables on the web, calculate DSo and DGo for the following reactions using:
DSo = SSoproducts - SSoreactants and
DGorxn=SDGoproducts - SDGoreactants
1. CH4 (g) + 2 O2 (g) ---------> CO2 (g) + 2 H2O (l)
a) DSo = SSoproducts - SSoreactants
Soproducts | Soreactants |
(1 mol CO2)(213.7 J/Kmol) = 213.7 J/K | (1 mol CH4)(186.1 J/Kmol) = 186.1 J/K |
(2 mol H2O)(69.940 J/Kmol) = 139.88 J/K | (2 mol O2)(205 J/Kmol) = 410 J/K |
SSoproducts= 353.58 J/K | SSoreactants = 596.1 J/K |
DSo= 353.58 J/K - 596.1 J/K = -242.52 J/K |
b) DGorxn=SDGoproducts - SDGoreactants
DGoproducts | DGoreactants |
(1 mol CO2)(-394.4 kJ/mol) = -394.4 kJ | (1 mol CH4)(-50.81 kJ/mol) = -50.81 kJ |
(2 mol H2O)(-237.192 J/Kmol) = -474.384 kJ | (2 mol O2)(0 kJ/mol) = 0 kJ |
SDGoproducts = -868.784 kJ | SDGoreactants= -50.81 kJ |
DGorxn= -868.784 kJ - (-50.81 kJ) = -817.974 kJ | spontaneous reaction |
2. 2 MgO (s) --------> 2 Mg (s) + O2 (g)
a) DSo = SSoproducts - SSoreactants
Soproducts | Soreactants |
(2 mol Mg)(32.69 J/Kmol) = 65.38J/K | (2 mol MgO)(26.9 J/Kmol) = 53.8 J/K |
(1 mol O2)(205 J/Kmol) = 205 J/K | |
SSoproducts = 270.38 J/K | SSoreactants = 53.8 J/K |
DSo = 270.38 J/K - 53.8 J/K = 216.58 J/K |
b) DGorxn=SDGoproducts - SDGoreactants
DGoproducts | DGoreactants |
(2 mol Mg)( 0 kJ/mol) = 0 kJ | (2 mol MgO)(-569.0 kJ/mol) = -1138.0 kJ |
(1 mol O2)( 0 kJ/mol) = 0 kJ | |
SDGoproducts = 0 kJ | SDGoreactants = -1138.0 kJ |
DGorxn= 0 kJ - (-1138.0 kJ) = +1138.0 kJ | nonspontaneous reaction |