Question

If ammonia is manufactured at 356 k, is the reaction spontaneous, given that the enthalpy and entropy change for the reaction are -93 kj/mol and -198 j/mol k, respectively?

Answer 1

The reaction will be spontaneous if Gibb free energy is negative, according the following relation:  
G = H - T*S  
where G is Gibbs free energy, T is change of enthalpy , T is temperature and S is change of entropy  
In the case of ammonia:  
G = -93000 - 356*(-198) = -93000 + 70488 = -22512 j/mol  
As G < 0 then the reaction is spontaneous.