The standard molar formation Gibbs functionThe standard molar formation Gibbs(G)function of chemical reaction1.The standard molar formation Gibbs function The standard molar Gibbs change of the reaction is derived from the formation of 1 mole substance B based on the elemental substance with reference state at temperature T(K).fGm(B,Phase,T)fGm(Refe.,T)=02.fGm calculation on the basis of fGm(B,Phase,T)For a chemical reaction,(B,Phase,298.15K)ifIt can only judge the reaction direction under the standard state.(1)To judge the direction of reaction and its limitsNonstandard state Standard state Direction of reaction and its limits rGm 0 rGm 0 rGm 0 Reaction couldnt be spontaneous rGm 0 rGm 0 equilibrium stateApplications of Gibbss free energy in the following aspects rHm 0,rSm 0,rGm 0 Exothermic and increased entropy,Reaction could be spontaneous.rHm 0,rSm 0 High T：rGm 0 Low T：rGm 0Exothermic and decreased entropy,Reaction could be spontaneous at low T.rHm 0 rSm 0 High T：rGm 0 Low T：rGm 0 Endothermic and increased entropy,Reaction could be spontaneous at high T.rHm 0 rSm 0 rGm 0 Endothermic and decreased entropy,Reaction couldnt be spontaneous.(2)to assess the stability of matters The greater the fGm(negative value),the stronger its stability.The relative smaller the fGm is,even the positive value,the weaker its stability.fGm is only related to temperature,in this way,the specific problems should be analyzed and treated concretely.Three ways to synthesize boron nitride：B(s)1/2N2(g)BN(s)rGm 228.4 kJmol1B2O3(s)2 NH3(g)2BN(s)3H2O(g)rGm 84.1 kJmol1BCl3(s)NH3(g)BN(s)3HCl(g)rGm 109.1 kJmol1pollution and corrosionExpensive cost(3)to provide a reasonable synthesis method(4)to estimate the transition temperature of the reactionrGm(T)rHm(T)TrSm(T)0 0 rHm 0 rSm 0 rGm 0 Exothermic and increased entropy,the reaction could be spontaneous.rHm 0 rSm 0 rGm 0Endothermic and decreased entropy,the reaction couldnt be spontaneous.