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The purpose is to determine the available energy. Some of the energy in any system is useless - can't be converted into useful work.
because, AMERICA!I'm a free man!
it is conventional to define gravitational potential energy (GPE) of object A to be 0 when the object is free from the gravitational field of object B (i.e. at a infinite distance away) As the objects get closer together, the GPE decreases, thus is less than 0. Therefore the GPE of any object normally has a negative value (however it all just depends on where you define to be the point at which the object has 0 GPE)
change in free energy is positive
Because they want to and it's a free country.
The Gibbs free energy will always be negative for a spontaneous reaction at constant temperature and pressure. This suggests that the reaction is thermodynamically favorable and can proceed without the input of external energy.
when H is negative and S is positive
Since the question seems to be about reactions - and the whole idea of a reaction is that something is changing... The CHANGE in Gibbs free energy will always be positive for a spontaneous reaction. As far as whether the Gibbs free energy of a system (without the term "change" attached) ... Since Gibbs free energy is a state function, it is always defined relative to a standard state. Asking if the Gibbs free energy is positive is akin to asking how "high" something is - the answer depends on where you define zero to be. If you define 0 height to be the level of the ground you are standing on, you will get a different answer than if you define zero height to be "sea level". A cactus in Death Valley may have a positive height relative to the ground, but would actually have a negative height relative to sea level. Likewise, the Gibbs free energy of a system will be positive or negative (or zero) depending on what you define as the standard state.
Since the question seems to be about reactions - and the whole idea of a reaction is that something is changing... The CHANGE in Gibbs free energy will always be positive for a spontaneous reaction. As far as whether the Gibbs free energy of a system (without the term "change" attached) ... Since Gibbs free energy is a state function, it is always defined relative to a standard state. Asking if the Gibbs free energy is positive is akin to asking how "high" something is - the answer depends on where you define zero to be. If you define 0 height to be the level of the ground you are standing on, you will get a different answer than if you define zero height to be "sea level". A cactus in Death Valley may have a positive height relative to the ground, but would actually have a negative height relative to sea level. Likewise, the Gibbs free energy of a system will be positive or negative (or zero) depending on what you define as the standard state.
Gibbs free energy and standard free energy are both measures of the energy available to do work in a chemical reaction. The main difference is that Gibbs free energy takes into account the temperature and pressure of the system, while standard free energy is measured under specific standard conditions. In chemical reactions, the change in Gibbs free energy determines whether a reaction is spontaneous or non-spontaneous. If the Gibbs free energy change is negative, the reaction is spontaneous, while a positive change indicates a non-spontaneous reaction. The relationship between Gibbs free energy and standard free energy lies in the fact that the standard free energy change can be used to calculate the Gibbs free energy change under any conditions.
The Gibbs free energy diagram helps determine if a chemical reaction is likely to occur by showing the energy changes involved. If the overall change in Gibbs free energy is negative, the reaction is thermodynamically feasible and likely to happen.
Gibbs free energy is important in determining if a phase transition, like water turning into ice or steam, will happen spontaneously. If the Gibbs free energy is negative, the transition is likely to occur without outside influence.
Yes, as long as the entropy of the universe increases.
A negative Gibbs free-energy value indicates that a reaction is spontaneous, meaning it can proceed without requiring external energy input. It suggests that the products of the reaction are more stable than the reactants at the given conditions.
it depends on the entropy and enathalpy of the reaction
The name of the single thermodynamic quantity is Gibbs free energy (G). The symbol for Gibbs free energy is ΔG (delta G). The sign of ΔG determines whether a reaction is spontaneous (negative ΔG) or non-spontaneous (positive ΔG).
For a spontaneous reaction, the numerical value of the Gibbs free-energy change (ΔG) is negative, indicating that the reaction is energetically favorable and will proceed in the forward direction. This negative ΔG means that the system is releasing energy and increasing in entropy during the reaction.