Chem Unit 8 Review - n/a PDF

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Aija Wint Prof. Grant Chem 100 Dec. 3, 2021 Unit 8a Review ● Bond dissociation energy is the energy that is required to break bonds in an atom. ● Energy is supplied by the surroundings to break bonds, Energy is released to the surroundings by the system during bond formation. ● Bond dissociation is an exothermic process. Bond Formation is an endothermic process. ● Endothermic reaction has more energy in the system than out. ● Exothermic reactions have more energy outside of the system than in. ● The difference in the potential energy of the products and reactants is known as enthalpy/^H. ● If delta H is negative it is exothermic. If delta H is positive it is endothermic. ● In a exothermic reaction the reactants have more potential energy than the products ● In an endothermic reaction the products have more potential energy than the products. ● Activation energy on an energy diagram is the difference in the potential energy of the reactants and the transition state on the graph required to break bonds. ● The addition of a catalyst to a chemical reaction will decrease the activation energy of a reaction because it provides a pathway for the reaction to occur with a lower potential energy. ● Entropy is the measure of disorder in a system. Gases have the most entropy of any state of matter. ● How to determine entropy in a process: ○ Phase change: if a state changes from a liquid/solid to a gas entropy increases. ○ Change in the number of moles from reactants to products. ● Spontaneous reactions with a -G are considered to be exergonic. Reactions with a positive G are considered to be endergonic. Unit 8B Review ● The Kinetic Molecular theory states that in order for reactions to occur particles: ○ Must collide with each other. ○ Must have a minimum amount of energy associated with them. ○ Must have the proper orientation. ● How fast a reaction occurs depends on the concentration of the reactants. ● Reaction rates increase as the temperature of the reaction increases. ● Adding a catalyst to reaction will also speed up the reaction time by providing an alternative pathway. ● Reactions that can make products (go forward) and reverse are considered reversible reactions. ● Once the rate of forming products equals the rate of forming reactants equilibrium is established and the concentration of the products and reactants remains constant.

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If the Kc is greater than one, that means that the concentration of the products is greater than the concentration of the reactants. Therefore, a forward reaction is preferred. If the Kc is less than one, that means that the concentration of the reactants is greater than the concentration of the products at equilibrium. Thus, a reverse reaction is favored Reactions with a Kc greater than one will be spontaneous (exergonic) in the forward direction and non spontaneous in the reverse direction (endergonic). The following stresses that can affect a reaction at equilibrium are: ○ Increasing or decreasing the reactant concentration ○ Increasing or decreasing the product concentration ○ Increasing or decreasing the temperature of the reaction mixture. ○ Increasing or decreasing the volume of the reaction vessel for gaseous reactions. Dissolution constants (Kd are temperature dependent) Non polar solutes will have a Kd = 0 in a polar solvent The dissociation constants for acids is Ka and the dissociation constants for bases is Kb. A insoluble salt will have Kd = 0...