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ΔG = ΔH - TΔS ΔG= Gibbs Free Energy ΔH = Enthalpy T = temperature in Kelvin ΔS = ENTROPY Physics Definition-Gibbs free energy, the amount of thermodynamic energy in a fluid system which can be converted into non-mechanical work at a constant temperature and pressure. What you need to know....If ΔG is negative, the a reaction is spontaneous (it can occur). Spontaneous does not imply that it is instantaneous. It could happen over the course of years or decades (I think you get the point). ΔG < 0 , the reaction is spontaneous ΔG maybe positive or negative under certain conditions. ΔG = ΔH - TΔS
Example of ΔH being + and ΔS + Regents Questions-highlight to reveal answers. 1. An Endothermic reaction may proceed spontaneously if there is an increase in A. Potential Energy B. Order C. Concentration D. Entropy
2. A reaction must be spontaneous if its occurrence is A.exothermic with an decrease in entropy B. exothermic with an increase in entropy C. endothermic with an decrease in entropy D. endothermic with an increase in entropy
3. Above 0oC, ice changes spontaneously to water according to the following equation: H2O(s) + heat --> H2O(l) The change in H2O(s) involve A. an absorption of heat and a decrease in entropy B. a release of heat and a decrease in entropy C. an absorption of heat and a increase in entropy D. a release of heat and a increase in entropy
4. A reaction must be spontaneous if the results in products that have A. lower potential energy and less randomness B. more potential energy and more randomness C. lower potential energy and more randomness D. more potential energy and less randomness
5. The change of the reactants into products will always be spontaneous if the products, compared to the reactants, have A. lower enthalpy and higher entropy B. higher enthalpy and higher entropy C. higher enthalpy and lower entropy D. lower enthalpy and lower entropy
6. As a solid dissolves in water, the temperature of the water decrease. the dissolving of this solid is A. endothermic and spontaneous B. endothermic and nonspontaneous C. exothermic and nonspontaneous D. exothermic and spontaneous
6. The ΔG of a chemical reaction refers to the change in A. entropy B. free energy C. state D. activation energy
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