25 C, 1 atm. There are reactions with large Delta G negative values. Delta G is the symbol for spontaneity, and there are two factors which can affect it, enthalpy and entropy. Enthalpy - the heat content of a system at constant pressure. D H > 0, D S > 0 This is an endothermic reaction with a positive entropy change. The amount of free energy released or consumed can be calculated from the equation $\Delta G = \Delta H - T\Delta S \label{eq1}$ with a small unknown value of $$\Delta H$$ and a large negative value of $$\Delta{S}$$, the value of $$\Delta G$$ will turn out to be positive. The two things to remember are: $\Delta G$ is a function of conditions and assumes an infinite amount of time. If the Delta G is positive, the reverse reaction (B ->A) is favored. The movement of any molecule or ion down — or up — a concentration gradient involves a change in free energy, ΔG ("Delta G") down releases energy so ΔG is negative; up consumes energy so ΔG is positive. If delta G is negative, the reaction is spontaneous, and if delta G is positive, the reaction is not spontaneous. But delta G naught is the delta G at standard condition. It can however be kinetically driven at leat in the short term. Link to a discussion of free energy changes. So delta G naught is constant for a given reaction. I need an explanation for why they are If a reaction has a positive $\Delta G$ it will not be thermodynamically driven. ∆G is the change in free energy K eq is the equilibrium constant (remember K eq = [products]/[reactants] ∆H is the change in enthalpy from reactants to products ∆S is the change in entropy (disorder) from reactants to products R is the gas constant (always positive) T is the absolute temperature (Kelvin, always positive) What it means: It is related to K at the equilibrium temp since then delta G is 0. 3. When delta G > 0 - It's a non-spontaneous reaction. As in: out of 10 steps of Glycolysis, 3 are irreversible steps. using delta G= -RTlnK where i have used T = 17 C, 35 C, 55 C, converted them into kelvin, R= 8.314 J/mol-K and langmuir constant value is less than 1, which makes them positive. Such a reaction is called endergonic. This sort of reaction is reactant-favored at low temperatures and product-favored at high temperatures. Entropy - the amount of disorder in the system. Unfavorable reactions have Delta G values that are positive (also called endergonic reactions). For Delta H, you cannot say. Below is a table to summarize it up! Conversely, a reaction with a positive value of D G is reactant-favored and requires the input of energy to go. With Delta G, it is absolute: Positive Delta G favors the reactants, and negative Delta G favors the products. A positive $$\Delta G$$ indicates that the mixing of the hydrophobe and water molecules is not spontaneous. There is a relationship between deltaG and equilibrium constant, K. 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