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30 Cards in this Set
- Front
- Back
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What is a Chemical Equalibrium?
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The condition in which the concentrations of all reactants and products in a closed system cease to change with time
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When does a C.E. occur?
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When opposing reactions are proceeding at equal rates
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What does it mean to say that opposing reactions are equal?
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The rate where products are formed from reactants equals the rate which reactants are formed from products. For equalibrium to occur. Neither products nor reactants can escape the system
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For Gasses what are concentrations expressed as?
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Partial pressures (in ATM)
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What are the two equations for Reaction rate (in gasses)
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Rate=k(P/RT)
Rate=k[A] |
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If "a" represents the reactants of an equation-
As Pa decreases... |
the rate of the forward reaction decreases
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At equalibrium what happens to the Partial Pressures of the products and reactants?
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They no longer change, the result is an Equilibrium mixture
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What does the double arrow in an equalibrium equation indicate?
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That the reaction is proceeding in both forward and backward directions (no net change to there amounts)
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What occurs to the ratio between products and reactants during Equal.
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The ratio has a constant value.
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What does the law of mass action express?
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the relationship between the concentrations(P.P. for gasses and M for solutions) of the reactants and products at equalibrium in any reaction.
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Keq=
(equalibrium constant expression) |
concentrations of products over concentrations of reactanats raised to the power of thier coefficients in a balanced equation
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What does the value of the Keq NOT depend on?
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initial amounts of rcts. or prods.
the presence of other substances as long as they dont react with a rct or prod. |
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What does the Keq vary with?
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Temperature
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IF the equalibrium constant is large what does this mean in regards to the composition of an equalibrium mixture?
(Keq>>1) |
Concentration of the products is higher (equal. lies to the right)
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What does a small equalibrium constant mean?
(keq<<1) |
Equalibrium lies to the left
(reactants dominant) |
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How can the equalibrium be approached?
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From either direction
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The Keq from one direction relates how to the other?
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The Keq of a rxn in reverse is the inverse of the Keq in the forward
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What is the net equalibrium constant?
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The priducts of the Eq. Constants for the indicidual steps
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How can you obtain the net equation
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mulitiply the keq of each
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The equalibrium constant of a rxn that has been multiplied by a number equals what?
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the Keq raised to a power = to that number
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The Keq for a net rxn is made up of how many steps?
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Two or more
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What are the units of Keq?
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Kew has no units assocuitated with it- this is because the values entered into the Keq are ratios (cancel out)
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What is a Homogeneous equilibria
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equalibrium involving substances all in the same phase
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What is Heterogeneous Equilibria?
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Equilibrium of substances in different phases
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Is it neccessary for pure solids or liquids to appear in Keq expression?
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No, because the reference concentration of any pure substance is simply that of the pure substance itself (division of such = 1)
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If a pure solid or liquid is involoved in a Heterogeneous equali...
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its concentration is not included in the equalibrium-constant expression for the rxn.
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What values are substituted in the Keq expression?
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Partial pressures for gasses and molar concentrations of dissolved species
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Pure solids, liquids, and solvents are....
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not included in equalibrium constant expression
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If we know the concentration of at least one species how can we dtermine others?
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Using stoichiometry of the rxn to deduce the equal. concentrations of others in the chemical equation
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What does the magnitude of Keq indicate?
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the extent to which a reaction will proceede
(eg. Keq large- heavy on right) |
