I am not able to understand the mathematical expression of "change in Gibbs free energy",(adsbygoogle = window.adsbygoogle || []).push({});

For a chemical reaction occurring at constant temperature and constant pressure,

(ΔS)_{total}= (ΔS)_{system}+ (ΔS)_{surrounding}

Considering that reaction is exothermic,ΔHbe the heat supplied by system to surrounding at constant pressure and temperature,

(ΔS)_{total}= (ΔS)_{system}+ (-ΔH)/T

- T * (ΔS)_{total}= ΔH - T * (ΔS)_{system}

The term on left hand side is known as Change in Gibbs free energyΔG. WHY?

also, the temperature in above expression isT, HOW?_{system}and not T_{surrounding }

(ΔS)should be_{surrounding}Q/T, where_{surrounding}Qis heat added to surrounding.

By intuition,ΔHamount of heat is available andT * ΔSis the unavailable energy. Thus_{system}(ΔH-T*ΔSis the amount of energy that is available to be converted to work and should be Gibbs free energy right? I am not able to understand it from the mathematical equation._{system})

Please explain what am I missing out? and where am I wrong? Please tolerate me for any mistakes, this is my first post and I do not have chemical engineering background. Thank you.

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# Gibbs free energy -- mathematical expression

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