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30 Cards in this Set

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What is a Chemical Equalibrium?
The condition in which the concentrations of all reactants and products in a closed system cease to change with time
When does a C.E. occur?
When opposing reactions are proceeding at equal rates
What does it mean to say that opposing reactions are equal?
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
For Gasses what are concentrations expressed as?
Partial pressures (in ATM)
What are the two equations for Reaction rate (in gasses)
Rate=k(P/RT)

Rate=k[A]
If "a" represents the reactants of an equation-
As Pa decreases...
the rate of the forward reaction decreases
At equalibrium what happens to the Partial Pressures of the products and reactants?
They no longer change, the result is an Equilibrium mixture
What does the double arrow in an equalibrium equation indicate?
That the reaction is proceeding in both forward and backward directions (no net change to there amounts)
What occurs to the ratio between products and reactants during Equal.
The ratio has a constant value.
What does the law of mass action express?
the relationship between the concentrations(P.P. for gasses and M for solutions) of the reactants and products at equalibrium in any reaction.
Keq=
(equalibrium constant expression)
concentrations of products over concentrations of reactanats raised to the power of thier coefficients in a balanced equation
What does the value of the Keq NOT depend on?
initial amounts of rcts. or prods.
the presence of other substances as long as they dont react with a rct or prod.
What does the Keq vary with?
Temperature
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)
What does a small equalibrium constant mean?
(keq<<1)
Equalibrium lies to the left
(reactants dominant)
How can the equalibrium be approached?
From either direction
The Keq from one direction relates how to the other?
The Keq of a rxn in reverse is the inverse of the Keq in the forward
What is the net equalibrium constant?
The priducts of the Eq. Constants for the indicidual steps
How can you obtain the net equation
mulitiply the keq of each
The equalibrium constant of a rxn that has been multiplied by a number equals what?
the Keq raised to a power = to that number
The Keq for a net rxn is made up of how many steps?
Two or more
What are the units of Keq?
Kew has no units assocuitated with it- this is because the values entered into the Keq are ratios (cancel out)
What is a Homogeneous equilibria
equalibrium involving substances all in the same phase
What is Heterogeneous Equilibria?
Equilibrium of substances in different phases
Is it neccessary for pure solids or liquids to appear in Keq expression?
No, because the reference concentration of any pure substance is simply that of the pure substance itself (division of such = 1)
If a pure solid or liquid is involoved in a Heterogeneous equali...
its concentration is not included in the equalibrium-constant expression for the rxn.
What values are substituted in the Keq expression?
Partial pressures for gasses and molar concentrations of dissolved species
Pure solids, liquids, and solvents are....
not included in equalibrium constant expression
If we know the concentration of at least one species how can we dtermine others?
Using stoichiometry of the rxn to deduce the equal. concentrations of others in the chemical equation
What does the magnitude of Keq indicate?
the extent to which a reaction will proceede
(eg. Keq large- heavy on right)