Question

Calculate ΔGº for the following reactions at 25ºC:

(a) N2(g) + O2(g) ---- 2NO(g)

(b) H2O(l) ---- H2O(g)

(c) 2C2H2(g) + 5O2(g) ----4CO2(g) + 2H2O(l)

Plese show clear step by step answers.

Answer 1

G^o of reaction is calculated as,

G^o = G^o_(product) - G^o_(reactant)

a) G^o =  G^o_{(2 NO)} - G^o_{( N2 + O2 )}

= (2 x 86.56 kJ/mol) - ( 0 kJ/mol + 0 kJ/mol)

= 173.12 kJ - 0 kJ/mol

= 173.12 kJ/mol

b) G^o =  G^o_{[H2O (g)]} - G^o  _[​_{H2O (l)]}

= ( - 228.58 kJ/mol ) - ( - 237.17 kJ/mol )

=  - 228.58 kJ/mol + 237.17 kJ/mol

= + 8.59 kj/mol

c)  G^o =  G^o_{[ (4 x CO2) + (2 x H2O (l)]}  - G^o  _{[​ (2 x C2H2) + ( 5 x O2) ]}

= [ ( 4 x - 394.38 kJ/mol) + ( 2 x - 237.17 kJ/mol ) ] - [ ( 2 x 209.2 kJ/mol) + (5 x 0 kJ/mol )]

= ( - 1577.52 kJ/mol + ( - 474.34 kJ/mol ) - ( 418.4kJ/mol + 0 kJ/mol)

= ( - 1577.52 kJ/mol - 474.34 kJ/mol ) - 418.4kJ/mol

= -2051.86 kJ/mol - 418.4 kJ/mol

= - 2470.26 kJ/mol