Mod 5 non equilibrium (1 Viewer)

[NexusRich]

For the non equilibrium dot point of the syllabus, I am not sure how to explain why photosynthesis and combustion are non equilibrium systems. I do know that photosynthesis has a decrease in entropy and increase in enthalpy, and is therefore non-spontaneous (positive Gibbs free energy) but what does that have to do with equilibrium ??? Also confused for combustion as well. Please explain, thanks for helping

 

[username_2]

For the non equilibrium dot point of the syllabus, I am not sure how to explain why photosynthesis and combustion are non equilibrium systems. I do know that photosynthesis has a decrease in entropy and increase in enthalpy, and is therefore non-spontaneous (positive Gibbs free energy) but what does that have to do with equilibrium ??? Also confused for combustion as well. Please explain, thanks for helping

Hmmm interesting question. It is important to remember that there are two components that allow a reaction to happen: the kinetics and the thermodynamics. Here we are specifically dealing with the thermodynamics, where two important terms are used to describe the conditions required for a reaction to either a) proceed in only one direct (irreversible system) or b) the products can become reactants and vice versa (equilibrium system). These terms are enthalpy - the energy required to break the system's bonds - and entropy which is much harder to pin down, but essential is the property of "greater randomness" which for the yr 12 chemistry level is generally determines by the no of moles components on each side and some others. The idea really is the a negative entropy favors a reaction to be non-reversible and a higher entropy favors a reaction to be non-reversible. But what if entropy is positive and entropy is positive, or entropy is negative and enthalpy is negative. Is the reaction reversible or not. To specifically balance the extent of the effects of each of the thermodynamic factors, the Gibbs Free Energy is introduced as a constant. It helps determine whether entropy is more significant in a reaction being irreversible (i.e. deltah < T*deltaS ) and vice versa. Hope this helps a bit and try to put this abit into the context of photosynthesis.

 

[jazz519]

Have a look here:

Q regarding non-equilibrium systems

If possible can someone explain how they would answer this question, "Explain why combustion and photosynthesis are examples of non-equilibrium reactions. Include an equation in your answer. "

boredofstudies.org

It is not really linked explicitly to entropy and enthalpy. It is about activation energy