The universe is described as the system and its surroundings Entropy is defined

# The universe is described as the system and its

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Law of Thermodynamics: the entropy of the universe is always increasing. The universe is described as the system and its surroundings. Entropy is defined as the ‘randomness’ or chaos in a system or object. Every substance has positive entropy at any temperature above zero Kelvin. Entropy is notated as ΔS and is measured in joules. Be careful to account for this when performing calculations with enthalpy and entropy, as enthalpy is measured in kJ. ΔS rxn = ΣΔS products - ΣΔS reactants 3 rd Law of Thermodynamics: the only object that has an entropy of zero is a perfect crystalline structure at a temperature of zero Kelvin. III.F. Gibbs Free Energy Gibbs free energy is defined as the energy associated with a chemical reaction that can do work. It is associated with the spontaneity of the reaction, and is affected by the value of K eq for the reaction, the E o cell , the enthalpy, and the entropy. Gibbs free energy is represented by ΔG and is measured in joules. It is a vector quantity, which means that a negative ΔG represents energy leaving the system, while positive ΔG represents energy entering the system. III.F.1. Spontaneity Spontaneity is a property of chemical formulas that describe their tendency to occur by themselves. A spontaneous reaction will occur without any external influences, but a nonspontaneous reaction requires external input to occur. When ΔG < 0, energy leaves the system when the reaction proceeds, and the reaction is spontaneous. When ΔG > 0, energy needs to enter the system for the reaction to proceed, and the reaction is nonspontaneous. III.F.2. Formulas The concept of Gibbs free energy ties together equilibrium, electrochemistry, and thermodynamics. ∆ܩ = ∆ܪ − ܶ∆ܵ ∆ܩ = −ܴ݈ܶ݊ܭ ∆ܩ = −݊ℱܧ ௖௘௟௟ ∆ܪ − ܶ∆ܵ = −ܴ݈ܶ݊ܭ = −݊ℱܧ ௖௘௟௟ .

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