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Entropy
based on notes
| Term | Definition |
|---|---|
| state function | a mathematical function that depends only on the initial and final states of the system |
| energy (equation) | ∆E = Ef - Ei |
| ∆E | change in energy of the system |
| Ef | final energy of the system |
| Ei | initial energy of the system |
| enthalpy (equation) | ∆H = Hf - Hi |
| ∆H | change in enthalpy of the system |
| Hf | final enthalpy of the system |
| Hi | initial enthalpy of the system |
| entropy (equation) | ∆S = Sf - Si |
| ∆S | change in entropy of the system |
| Sf | final entropy of the system |
| Si | initial entropy of the system |
| Entropy | the measure of disorder (dispersal) present in a system, the extent of randomness in a system |
| the Third Law of Thermodynamics | the entropy of a pure crystalline substance at absolute zero is zero; no disorder and no movement means no entropy |
| the Second Law of Thermodynamics | for any spontaneous process, the entropy of the universe will increase; ∆S universe > 0 |
| entropy of a phase change (equation) | ∆S phase change (in J/K) = ∆H phase change (in J) / T (in K) |
| spontaneous change | a change that can occur without work being done to bring it about; can occur on its own; is irreversible |
| nonspontaneous change | a change that can only be brought about by doing work |
| ∆S positive | entropy of system increased; ∆S > 0; Sf > Si |
| ∆S negative | entropy of system decreased; ∆S < 0; Sf < Si |
| Gibbs Free Energy (equation) | ∆G = ∆H - T∆S |
| ∆G | change in Gibbs Free Energy of the system |
| ∆G<0 | ∆G is negative, reaction is spontaneous |
| ∆G=0 | reaction is at equilibrium |
| ∆G>0 | ∆G is positive, reaction is nonspontaneous |
| temperature in Kelvins | always positive |
| ∆H>0 | ∆H is positive, reaction is endothermic |
| ∆H<0 | ∆H is negative, reaction is exothermic |
| ∆S>0 | ∆S is positive, entropy is increasing |
| ∆S<0 | ∆S is negative, entropy is decreasing |
| ⁻∆H, ⁺∆S | reaction is spontaneous at all temperatures |
| ⁻∆H, ⁻∆S | reaction is spontaneous only at low temperatures |
| ⁺∆H, ⁺∆S | reaction is spontaneous only at high temperatures |
| ⁺∆H, ⁻∆S | reaction is nonspontaneous at all temperatures |
| When ∆G=0 | ∆S = ∆H/T |
Created by:
ccons
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