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.
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.
The formation of liquid bromine is spontaneous when the Gibbs free energy change for the process is negative, which occurs when ΔG < 0. This means the temperature must be within the range where ΔG is negative, which typically corresponds to temperatures above the boiling point of bromine (~332K) where the entropy term dominates over the enthalpy term in the Gibbs free energy equation.
In adsorption, Gibbs free energy decreases because the adsorbate molecules are attracted to the surface of the adsorbent, reducing the overall energy of the system. This leads to a more stable configuration with a lower free energy. The decrease in Gibbs free energy indicates that the adsorption process is spontaneous at a given temperature and pressure.
-225.3 KJ