chemical

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chemical equilibrium!
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First, a metaphor
Two floors of a store are connected by up and
down escalators
Floor 1 has 7 people, floor 2 has 12 people.
There are always 2 people occupying each escalator
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Floor 2 7 people
Floor 1 12 people
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Floor 2 7 people
2 people on the up escalator
Floor 1 12 people
2 people on down escalator
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Floor 2 7 people
2 people on the up escalator
Floor 1 12 people
2 people on down escalator
Question 1 if there are always two people
on each escalator at any one moment, will the
amount of people on each floor ever change?
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Floor 2 7 people
2 people on the up escalator
Floor 1 12 people
2 people on down escalator
Question 2 if there are always two people
on each escalator at any one moment, will the
specific people occupying each floor ever change?
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The double arrow tells us that this reaction can
go in both directions
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1) Reactants react to become products,
N2 3H2 2NH3
(forward reaction)
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1) Reactants react to become products,
N2 3H2 2NH3
(forward reaction)
while simultaneously,
2) Products react to become reactants
N2 3H2 2NH3
(reverse reaction)
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In a closed system, where no reactants,
products, or energy can be added to or removed
from the reaction, a reversible reaction will
reach equilibrium.
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At equilibrium, the rate of the forward
reaction becomes equal to the rate of the reverse
reaction, and so, like our escalator metaphor,
the two sides, reactants and products, will have
constant amounts, even though the reactions
continue to occur.
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However (like the metaphor), the equilibrium
amounts of reactants and products are usually
not equal, they just remain unchanged.
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N2 3H2 2NH3
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N2 3H2 2NH3
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N2 3H2 2NH3
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N2 3H2 2NH3
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
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reverse
forward
etc! the reactions go on continuously in both
directions.
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Changes in the concentrations of the reactants
and products can be graphed the graph indicates
when equilibrium has been reached.
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
concentration
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
N2
H2
concentration
NH3
time
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
N2
H2
concentration
NH3
time
Question 3 at what point has equilibrium been
established?
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
N2
H2
concentration
NH3
time
Question 4 what does the graph tell you about
the concentration of each species once
equilibrium is established?
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For N2 3H2 2NH3, suppose you begin with
the following N2 1 M, H2 1 M, and NH3 0
M
N2
H2
concentration
NH3
time
Question 5 what might a rate vs time graph look
like for the above reaction?
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For and
still beginning with
N2 1 M, H2 1 M, and NH3 0 M
rate
time
Question 5 what might a rate vs time graph look
like for the above reaction?
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For and
still beginning with
N2 1 M, H2 1 M, and NH3 0 M
rate
time
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For and
still beginning with
N2 1 M, H2 1 M, and NH3 0 M
forward
rate
reverse
time
Question 6 at what point has equilibrium been
established?
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N2
forward
H2
rate
concentration
reverse
NH3
time
time
Question 7 describe how the two graphs are
related.
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N2
forward
H2
concentration
reverse
NH3
time
Question 8 do either of the two graphs indicate
if Keq gt1 or Keq lt1?