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Study Guide: General Biology

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Study Guide: General Biology
Chapter 6
Explain what free energy is and how it can be used to predict the energetic outcome of chemical reactions.Free energy is defined as the energy available to do work in any system. The free energy is denoted by the symbol G. G = H – TS* H: the energy contained in a molecule’s chemical bonds, called enthalpy.* TS: the energy term related to the degree of disorder in the system. T is the absolute temperature (K), and S is the entropy.We can use the change in free energy to predict whether a chemical reaction is spontaneous or not:- G positive: the products contain more free energy than the reactants. The bond energy (H) is higher, or the disorder (S) is lower. Therefore, the reaction is NOT spontaneous because it requires the input of energy endergonic. - G negative: the products have less free energy than the reactants. Either the bond (H) is lower, or the disorder (S) is higher; or both. Such reactions tend to proceed spontaneously. These reactions release the excess of free energy as heat exergonic.
State the first and second laws of thermodynamics and explain how those laws relate to chemical processes.1) First Law of Thermodynamics: it concerns the amount of energy in the universe. Energy cannot be created or destroyed; it can only change from one form to another. The amount of energy in the universe remains constant. Potential energy can be transformed into kinetic energy; and some energy dissipates into the environment as heat, which is the measure of the random motion of molecules. Heat can only be harnessed to do work only when there is a heat gradient – a temperature difference between two areas. The energy available to do work decreases, as more of it is progressively lost as heat.2) Second Law of Thermodynamics: it concerns the transformation of potential energy into heat, or random molecular motion. It states that the disorder in the universe, entropy, is continuously increasing. Energy transformations proceed spontaneously to convert

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