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### 39 Cards in this Set

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 Absolute entropy of a substance the entropy of a substance relative to its entropy in a perfectly ordered crystalline form at 0 K Bomb Calorimeter A device used to measure the heat transfer between system and surroundings at constant volume Bond Energy the amount of energy necessary to break one mole of bonds in a gaseous substance, to form gaseous products at the same temperature and pressure Calorimeter a device used to measure the heat transfer that accompanies a physical or chemical change endothermic process a process that absorbs heat enthalpy change, change in H the quantity of heat transferred into or out of a system as it undergoes a chemical or physical change at constant temperature and pressure entropy, S A thermodynamic state property that measures the degree of disorder or randomness of a system equilibrium a state of dynamic balance in which the rates of forward and reverse processes(reactions) are equal; the state of a system which neither the forward nor the reverse process is thermodynamically favored. Exothermic process a process that gives off(releases) heat First Law of Thermodynamics the total amount of energy in the universe is constant(also known as the Law of Conservation of Energy); energy is neither created nor destroyed in ordinary chemical reactions and physical changes. Gibbs free energy, G The thermodynamic state function of a stystem that indicates the amount of energy available for the system to do tuseful work at constant T and P. It is defined as G= H-TS Gibbs free energy change, change in G the indicator of spontaneity of a process at constant T and P. Change in G= change in H - T times the change in S. If the change in G is negative, the process is product-favored(spontaneous). Hess's Law of Heat Summation The enthalpy change for a reaction is the same wheter it occurs in one step or a series of steps. Internal Energy, E All forms of energy associated with a specific amount of a substance Law of Conservation of Energy Energy cannon be created or destroyed in a chemical reaction or in a physical change; it may be changed from one form to another. See first law of thermodynamics Mole of reaction( mol rxn) the amount of reaction that corresponds to the number of moles of each substance shown in the balanced equation Nonspontaneous change reactant-favored change pressure-volume work work done by a gas when it expands against an external pressure or work done on a system as gases are compressed or consumed in the presence of an external pressure Product-favored change a change for which the collection of products is more stable than the collection of reactants under the given conditions; also called spontaneous change reactant-favored change a change for which the collection of reactants is more stable than the collection of preoducts under the given conditionsl; also called nonspontaneous change. Second Law of Thermodynamics the universe tends toward a state of greater disorder in spontaneous processes Spontaneous change see product-favored change Standard enthalpy change, change in H^0 the enthalpy change in which the number of moles of reactants specirfied in the balanced chemical equation, all at standard states, is converted completely to the specified number of moles of products, all at standard states, is converted completely to the specified number of moles of products, all at standard states Standard entropy change, change in S^0 Teh entropy change in which the number of moles of reactants specified in the balanced chemical equation, all at standard states, is converted completely to the specified number of moles of products, all at standard states. Standard molar enthalpy of formation, change in H^0, f subscript(of a substance) the enthalpy change for the formation of one mole of a substance in a specified state from its elements in their standard states; also called standard molar heat of formation or just heat of formation. Standard molar entropy, S^0(of a substance) The absolute entropy of a substance in its standard state at 298 K Standard reacton a reaction in which the numbers of moles of reactants shown in the balanced equation, all in their standard states, are completely converted to the numbers of moles of products shown in the balanced equation, also all at their standard states. Standard state( of a substance) See thermodynamic state of a substance State function a variable that defines the state of a system; a function that is independent of the pathway be which a process occurs Surroundings Everythin in the environment of the system Stystem the substances of interest in a process; the part of the universe under investigation Thermochemical equation a balanced chemical equation together with a designation of the corresponding value of change in H reaction. Sometimes used with chagnes in other thermodynamic quantities Thermochemistry the observation, measurement, and prediction of energy changes for both physical changes and ch emical reactions Thermodynamics the study of the energy transfers accompanying physical and chemical processes Thermodynamic state of a system a set of conditions that completely specifies all of the properties of the system Thermodynamic standard state of a substance The most stable state of the substance at one atmosphere pressure and at some specific temperature(25 degress celsius unless otherwise specified). Third Law of Thermodynamics the entropy of a hypothetical pure, perfect, crystalline substance at absolute zer temperature is zero Universe the system plus the surroundings Work the application of a force through a distance; for physical changes r chemical reactions at constant external pressure, the work done on the system is -P change in V; for chemical reactions that involve gases, the work done on the system can be expressed as -(change in n)RT.