# Module 13: Thermodynamics

 When a reaction is exothermic, energy will be thought of as ______________.
 When a reaction is exothermic, energy will be thought of as a product in the reaction. (417)
 When a reaction is exothermic, energy will be considered _______________.
 When a reaction is exothermic, energy will be considered a reactant. (417)
 The energy stored in a substance is called the ___________ of that substance.
 enthalpy(symbol: H)
 Change in Enthalpy (?H)
 The energy change that accompanies a chemical reaction. (419)
 1 calorie = ________ Joules
 1 calorie = 4.184 Joules (419)
 ΔH is [positive/negative] for endothermic reactions.
 positive (419)
 ΔH is [positive/negative] for exothermic reactions.
 negative (419)
 Bond energy
 The energy required to break a bond. (424)
 Hess’s Law
 Enthalpy is a state function and is therefore independent of path. (429)
 State function
 Any quantity that depends solely on the final destination, not on the way you get to that destination. (429)
 Enthalpy of formation (;Hf)
 The ;H of a formation reaction. (430)
 ; What are standard enthalpies of formation?
 Standard conditions under which most chemistry is done: room temperature (25; Celsius) normal atmospheric pressure (1.00 atm) (430)
 In the symbol ;Hf0 what does the “0” tell you?
 That the enthalpy of formation was measured under standard conditons. (430) ;
 What is the standard enthalpy of formation of an element in its elemental form?
 zero (431)
 Energy diagram
 Diagram that shows: the energy of the reactants intermediate state products; in a chemical reaction. (436)
 Reaction coordinate
 Coordinate which tells how close the reaction is to completion. (436)
 Intermediate state
 A complex formed in the process of a chemical reaction when the reactants and products are interacting. (436)
 Activated complex
 Another name for the intermediate state of a chemical reaction. (436)
 Activation energy
 The energy necessary to start a chemical reaction. (437)
 Entropy
 A measure of the disorder that exists in any system. (437)
 Second Law of Thermodynamics
 The entropy of the universe must always either increase or remain the same.; It can never decrease. (440)
 What are the relative entropy phases of matter? (solid, liquid, gas) ;
 solid (least amount of entropy) liquid (greater amount of entropy) gas (highest amount of entropy) (441)
 With rising temperature, the entropy of a system [increases/decreases].
 increases (441)
 As the matter it contains increases, the entropy of a system [increases/decreases.
 increases (441)
 Second Law of Thermodynamics (mathematical equation)
 ;Suniverse ; 0 ; (442)
 All substances, even elements, have ___________________.
 an absolute entropy. (443)
 Gibbs Free Energy (;G)formula
 ;G = ;H – T;;S ; (446)
 Standard enthalpy of formation
 The ;H of a formation reaction at T = 298 K and P = 1.00 atm (430)
 A reaction that is consistent with the Second Law of Thermodynamics is said to be ____________.
 spontaneous (446)
 A reaction is called;not spontaneous when it is not consistent with the Second Law of Thermodynamics because ____________.
 the reaction cannot occur. (446)
 When ;G ; 0, then the reaction is consistent with the Second Law, and is therefore _____________.
 spontaneous. (447)
 If ;G ; 0, then the reaction cannot proceed, because it violates __________________.
 the Second Law of Thermodynamics. (447)
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