Transcript Reaction Equilibrium

Regent’s Warm-Up
A substance is classified as an
electrolyte because
(1) it has a high melting point
(2) it contains covalent bonds
(3) its aqueous solution conducts an electric
current
(4) its aqueous solution has a pH value of 7.
Regent’s Warm-Up
A substance is classified as an
electrolyte because
(1) it has a high melting point
(2) it contains covalent bonds
(3) its aqueous solution conducts an electric
current
(4) its aqueous solution has a pH value of 7.
Reaction Equilibrium
Aim: What Is Reaction
Equilibrium?
Do Now: What Controls
Equilibrium in
the Body? How?
Reaction Equilibrium
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Equilibrium in Chemistry refers to a
balance between products and reactants
MOST chemical reactions are reversible,
which means can go in the forward
direction and form products or in the
reverse direction and form reactants.
Reaction Equilibrium
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Once a rxn starts the fwd
rxn over time will slow
down or the rate of the
fwd reaction decreases
In the example, the
concentration of
reactants A and B will
decrease as the reaction
goes in the fwd direction,
while the products C and
D increases
Reaction Equilibrium
As the rate of the fwd
reaction decreases the
rate of the rev reaction
begins to increase
 After time the rates of the
fwd and rev rxns will
become equal
 When the rates are equal
the concentrations of
reactants and products
will no longer CHANGE
 THIS IS CALLED A
DYNAMIC EQUILIBRIUM
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Reaction Equilibrium
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The concentrations of
reactants and products
are NOT equal in a
dynamic equilibrium
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If at equilibrium the
PRODUCTS are
greater the FORWARD
reaction is favored
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That means in our
example the
concentrations of C
and D will be greater
than A and B
Reaction Equilibrium
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If at equilibrium the
REACTANTS are
greater the REVERSE
reaction is favored
That means in our
example at equilibrium
the concentrations of A
and B will be greater
than C and D
Reaction Equilibrium
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Therefore Dynamic
Equilibrium occurs
when opposing rates
are equal (rate of fwd
reaction = rate of rev
reaction)
The Law of Mass
Action expresses the
position of equilibrium
numerically
Reaction Equilibrium
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Therefore Dynamic
Equilibrium occurs
when opposing rates
are equal (rate of fwd
reaction = rate of rev
reaction)
The Law of Mass
Action expresses the
position of equilibrium
numerically
Reaction Equilibrium
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Let’s try some equilibrium basics
Which statement correctly describes a chemical
reaction at equilibrium?
1. The concentrations of the products and reactants are equal.
2. The rate of the forward reaction is less than the rate of the
reverse reaction.
3. The concentrations of the products and reactants are constant.
4. The rate of the forward reaction is greater than the rate of the
reverse reaction.
Reaction Equilibrium

Let’s try some equilibrium basics
Which statement correctly describes a chemical
reaction at equilibrium?
1. The concentrations of the products and reactants are equal.
2. The rate of the forward reaction is less than the rate of the
reverse reaction.
3. The concentrations of the products and reactants are constant.
4. The rate of the forward reaction is greater than the rate of the
reverse reaction.
Reaction Equilibrium
For a chemical reaction is at equilibrium.
Compared to the rate of the forward reaction,
the rate of the reverse reaction is:
1. faster and more reactant is produced
2. the same and the reaction has stopped
3. faster and more product is produced
4. the same and the reaction continues in both
directions
Reaction Equilibrium
For a chemical reaction is at equilibrium.
Compared to the rate of the forward reaction,
the rate of the reverse reaction is:
1. faster and more reactant is produced
2. the same and the reaction has stopped
3. faster and more product is produced
4. the same and the reaction continues in both
directions
Reaction Equilibrium
Given the equilibrium reaction at STP: . . .
Which statement correctly describes this
system?
1. The forward and reverse reaction rates are equal.
2. The concentrations of N2O4 and NO2 are equal.
3. The forward and reverse reaction rates are both
increasing.
4. The concentrations of N2O4 and NO2 are both
increasing.
Reaction Equilibrium
Given the equilibrium reaction at STP: . . .
Which statement correctly describes this
system?
1. The forward and reverse reaction rates are equal.
2. The concentrations of N2O4 and NO2 are equal.
3. The forward and reverse reaction rates are both
increasing.
4. The concentrations of N2O4 and NO2 are both
increasing.
Reaction Equilibrium
Which factors must be equal in a reversible
chemical reaction at equilibrium?
1. the activation energies of the forward and
reverse reactions
2. the concentrations of the reactants and products
3. the rates of the forward and reverse reactions
4. the potential energies of the reactants and
products
Reaction Equilibrium
Which factors must be equal in a reversible
chemical reaction at equilibrium?
1. the activation energies of the forward and
reverse reactions
2. the concentrations of the reactants and products
3. the rates of the forward and reverse reactions
4. the potential energies of the reactants and
products