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Q: When will Gibbs free energy always be positive or negative?
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According to the Gibbs free energy equation G H - TS when is a reaction always spontaneous?

when H is negative and S is positive


What will Gibbs free energy always be 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.


What reactions will Gibbs free energy always be 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.


Is cellular respiration a negative or positive delta g?

Photosynthesis is a positive delta G as it produces more free energy than it uses. The overall result of the Gibbs equations shows that delta G is positive


Is polymerization endothermic or exothermic?

Exothermic, because the reaction enthalpy must be negative. With polymerization, the entropy decreases. The Gibbs energy has to be negative. Thus negative reaction enthalpy. Gibbs energy = reaction enthalpy - temperature*entropy


What is a negative Gibbs free-energy value an indication of?

Spontaneous reaction


An endergonic reaction is a reaction in which the change in Gibbs free energy is what?

Positive (greater than 0).


How can you decide whether a chemical process is spontaneous?

Whether or not a chemical process is spontaneous is determined by a variable named the Gibbs' free energy, or just Gibbs' energy, given by the formula G = H - TS, where G is the Gibbs' energy, H is enthalpy, T is temperature and S is entropy. A negative G implies that the chemical process is spontaneous and will occur by itself, and a positive G implies that energy is required to make the reaction occur.


True or False A large positive value of entropy tends to favor products of a chemical reaction?

True, a large positive value of entropy tends to favor products of a chemical reaction. However, entropy can be offset by enthalpy; a large positive value of enthalpy tends to favor the reactants of a chemical reaction. The true measure to determine which side of a chemical reaction is favored is the change in Gibbs' free energy, which accounts for both entropy and enthalpy, as calculated by: Change in Gibbs = Change in Enthalpy - Temp in Kelvin * Change in Entropy A negative value of Gibbs free energy will always favour the products of a chemical reaction.


Is the Gibbs free energy negative in the spontaneous reaction?

Yes, as long as the entropy of the universe increases.


What is the name and symbol of the single thermodynamic quantity which determines whether or not a reaction is spontaneous?

Gibbs free energy -- symbol G. If the change in Gibbs free energy for a reaction is negative, the reaction is spontaneous. If it is zero, you are at equilibrium. If it is positive, the reaction is NOT spontaneous.G ≡ H -TS (or in another useful form dG = dH -TdS)whereH is enthalpyT is absolute temperatureS is entropy


What happens in an endergonic reaction?

An endergonic reaction is a chemical reaction in which the standard change in free energy is positive.