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Unformatted text preview: 183 Chemical Equilibrium 17 17-1 (a) reversible reaction : a reaction that can occur in either direction and does not go to completion. Such reactions reach equilibrium with significant amount of reactants and products remaining. (b) static equilibrium : a state of balance that exists when all acting influences are canceled, so there are no micro changes. (c) equilibrium constant, K : a quantity that describes the position of equilibrium for a reversible reaction. It is equal to the product of the equilibrium concentrations of the products divided by the product of the equilibrium concentrations of the products, each raised to the power that corresponds to its coefficient in the balanced chemical equation. 17-3 Equilibrium exists when all acting influences are canceled by others, resulting in a balanced system. In a static equilibrium there are no micro changes caused by the influences. In a dynamic equilibrium there are micro changes but the changes occur in such a way that the net result is that the system remains unchanged. Chemical equilibria are dynamic equilibria ; individual molecules are continually reacting, even though the overall composition of the reaction mixture does not change. 17-5 (a) A very large value of K indicates that the reaction proceeds far toward completion (or that the forward reaction is highly favored over the reverse reaction). The equilibrium mixture has much higher concentrations of products than of reactants. (b) A very small value of K indicates that the reaction proceeds only very slightly (or that the reverse reaction is highly favored over the forward reaction). The equilibrium mixture has much higher concentrations of reactants than of products. (c) A value of K of about 1 indicates that the forward and reverse reactions are about equally favored. The equilibrium mixture contains about equal concentrations of products and reactants, if they are raised to the same power. 17-7 At equilibrium the rates of opposing processes are equal. Putting it another way: when the rates of opposing processes become equal, the system arrives at a state of equilibrium. 17-9 The equilibrium constant is the product of the equilibrium concentrations of the products divided by the product of the equilibrium concentrations of reactants, each raised to the power that corresponds to its coefficient in the balanced equation. When using the value of an equilibrium constant, it is necessary that we also know the balanced chemical equation since the powers of the terms in the equilibrium constant are tied to the coefficients in the balanced equation. For example, the following two equations have different values for their equilibrium constants....
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