Question

What is the Gibbs free energy change at 25°C for the reaction: 2NO(g) + O2(g) → 2NO2(g) given that the standard Gibbs free energy of formation of NO, O2, and NO2 are +90.4 kJ/mol, 0 kJ/mol and +51.3 kJ/mol, respectively?

Answer 1

To calculate the Gibbs free energy change  G  for the reaction, we can use the following equation:G =  Gf products  -  Gf reactants where Gf represents the standard Gibbs free energy of formation of the respective compounds.For the given reaction:2NO g  + O2 g   2NO2 g G = [2  Gf NO2 ] - [2  Gf NO  + Gf O2 ]We are given the standard Gibbs free energy of formation for NO, O2, and NO2 as +90.4 kJ/mol, 0 kJ/mol, and +51.3 kJ/mol, respectively.Substitute the given values into the equation:G = [2   +51.3 kJ/mol ] - [2   +90.4 kJ/mol  + 0 kJ/mol]G = [102.6 kJ/mol] - [180.8 kJ/mol]G = -78.2 kJ/molThe Gibbs free energy change at 25C for the reaction is -78.2 kJ/mol.