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33 Cards in this Set
- Front
- Back
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Chemical Equilibrium |
A chemical reaction can acheive a state in which the forward and reverse processes are occurring at the same rate. |
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A chemical equilibrium results in... |
The formation of an equilibrium mixture of the reactants and products of the reaction. |
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The composition of an equilibrium mixture does not... |
The composition of an equilibrium mixture does not change with time. |
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The Haber Process |
? |
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The relationship among the concentrations of the reactants and the products of a system at equilibrium is given by... |
The law of mass action |
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For a general equilibrium equation of the form aA+bB<>pP+qQ this law states that we can write the following equilibrium-constant expression: |
Kc=[P]^p[Q]^q/[A]^a[B]^b |
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The equilibrium-constant expression depends only on the... |
stoichiometry of the reaction |
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For a system at equilibrium at a given temperature, Kc will be a constant called… |
the equilibrium constant |
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The subscript c of Kc equilibrium constant indicates that… |
the concentrations of reactants and products are expressed in molarity |
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If concentrations are indicated as pressures... |
The equilibrium constant is denoted Kp |
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The values of the constants Kc and Kp are related by the following equation: |
Kp=Kc(RT)^moles of gaseous products minus moles of gaseous reactants |
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The value of the equilibrium constant changes with… |
temperature |
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A large value of equilibrium constant Kc or Kp indicates... |
that the equilibrium mixture contains more products than reactants. |
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A small value of for the equilibrium constant indicates... |
that the equilibrium lies toward the reactant side. |
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The equilibrium constant expression and the equilibrium constant of the reverse of a reaction are... |
the reciprocals of those of the forward reaction. |
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Section 15.3: Heterogeneous Equilibria
Homogeneous Equilibria |
Equilibria for which all substances are in the sam phase. |
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Heterogeneous Equilibria |
Two or more phases are present. |
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Because the concentrations of pure solids and liquids are constant... |
these substances are left out of the equilibrium-constant expression for a heterogeneous equilibrium. |
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Section 15.4: Calculating Equilibrium Constants
If the concentrations of all species in an equilibrium are known, |
the equilibrium-constant expression can be used to calculate the value of the equilibrium constant. |
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15.4: Calculating Equilibrium Constants The changes in the concentrations of reactants and products on the way to achieving equilibrium will be governed by… |
the stoichiometry of the reaction. |
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15.5: Applications of Equilibrium Constants
The reaction quotient, Q, is found by |
substituting reactant and product concentrations into the equilibrium-constant expression. |
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15.5: Applications of Equilibrium Constants
Q=K |
The system is at equilibrium |
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Q=\K |
The system is not at equilibrium. |
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When Q < K |
The reaction will move toward equilibrium by forming more products (the reaction forms from the left to the right) |
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When Q > K |
The reaction moves from right to left. |
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Knowledge of the value of Kc or Kp permits |
the calculation of the equilibrium concentrations of reactants and products, often by the solution of an equation in which the unknown is the change in a concentration. |
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15.6: Le Châtelier's Principle
Le Châtelier's Principle states |
that if a system at equilibrium is disturbed, the equilibrium will shift to minimize the disturbing influence. |
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If a reactant or product is added to a system at equilibrium, |
the equilibrium will shift to consume the added substance. |
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The effects of removing reactants or products and of changing the pressure or volume of a reaction in equilibrium |
can be similarly deduced with the Châtelier Principle. |
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The change in enthalpy for a reaction indicates |
how an increase in temperature affects the equilibrium. |
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For an endothermic reaction an increase in temperature |
shifts the equilibrium to the right. |
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For an exothermic reaction a temperature increase |
shifts the equilibrium to the left. |
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Catalysts affect |
the speed at which equilibrium is reached but do not affect K. |
