Equilibrium Notesheets
Name______________________________
Period______Date____________________
The Concept of Equilibrium Ex)
1. Reversible Reactions: Chemical reaction in which the _________________ can regenerate the original
______________________. A ____________________ arrow is used to express a reversible reaction.
Ex)
2NO2(g) ↔
reactants yield
N2O4(g)
products


or





 forward reaction
or

 reverse reaction
Forward Rxn: __________________________ Reverse Rxn: ________________________________
2. Some reactions can reverse ___________________________, some under certain ________________,
( ___________________, pressure or a catalyst) and some will _________ reverse.
3. Chemical Equilibrium: State of a product’s and reactant’s concentrations remaining _______________,
not _______________. This is because the ___________ of the forward and reverse reactions are
______________. The symbol “[ ]” denotes __________________________.
A. Reaction rates are affected by _____________________. If the concentration of the
reactant increases, the rate of the forward reaction will ___________________.
B. As the reaction proceeds, the concentration of the reactants __________________ and the
products ________________. This will cause the forward reaction to _________________.
4. Reaching equilibrium does _____ mean the reaction has _______________. It only means the
__________ of the forward and reverse reactions are ______________. This is not a static equilibrium,
but a __________________ equilibrium that stays _________________ over time.
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Reaction Rates & Equilibrium:
A. Collision Theory: (Theoretical Model)
1. In order for reactions to occur between substances, the particles must ____________________.
2. According to the ___________________ _______________, a successful collision occurs when
A. the collision is _______________________ enough, and
B. the particles collide with the correct ___________________________
3. Effective collisions____________ to the formation of products; ineffective collisions
do __________ lead to the formation of products.
4. A successful collision results in bond _____________________ (endothermic) and
bond _______________________ (exothermic).
5. The minimum energy needed to produce an effective collision is called the
____________________ ______________ for the reaction. It’s abbreviation is _________.
6. A transitional structure results from a successful collision. The structure is present while old
bonds are ___________________ and new bonds are ___________________.
It is called an _____________________ ______________ and is unstable and short-lived.
It is neither ___________________ nor ____________________.
7. A substance that increases the rate of a chemical reaction by providing a mechanism with a
lower energy of activation is called a _______________________.
8. A system that has just one phase is called a ___________________________ system, while a
system that has more than one phase is called a _______________________________ system.
9. Energy Diagram: shows changes in ________________ during a reaction.
10. Sketch of Endothermic
and
Exothermic Reactions
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Energy Diagram for a Chemical Rxn.
Course of Reaction
Factors Affecting Reaction Rates
1. Chemical Kinetics is concerned with the ______________ at which a reaction occurs.
2. ____________________ ______________ is a measure of the rate or speed of a chemical reaction.
Reaction rate is determined by measuring the change in _________________________ of
reactants and products over a certain amount of ______________. These reaction rates are determined
experimentally.
3. Rate-influencing factors are those factors that affect rate of reactions by altering the
___________________, ____________________, or ________________ at which particles collide.
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4. According to the Collision Theory, the following ______ factors affect the rate of a reaction:
1. Nature of Reactants:
A. Structure: __________________ of bonds broken/formed & the __________________
B. State: Homogeneous systems have reactants and products in the ______________ state.
Heterogeneous systems have reactants and products in ________________ states.
Homogeneous systems usually react _______________ and heterogeneous
systems react __________________.
2. Temperature: (___________________________________) Rule of thumb is that every _____
_______________ in temperature ____________________________________
3. Concentration: _____________________ concentration __________________ # of collisions.
Aqueous solutions can change [conc.] or _________________, gases can
change __________________. Solids and pure liquids like __________ cannot
change concentration.
4. Surface Area: _______________surface area _______________frequency of collisions. This is
especially true for ______________________ systems ( _______________.)
5. Catalyst:
Increases the rate of reaction without being _______________________ in the
reaction. Catalysts speed up the reaction
rate by ______________________ the
______________________
_______________ needed for the
reaction to occur.
5. Inhibitors: ____________________ the rate of the reaction
by taking the place of a ____________________ and
_________________ the reaction (opposite of a catalyst.)
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Equilibrium Systems and Stress – Le Chatlier’s Principle
1. Le Chatelier’s Principle states that if a stress is imposed on a system at equilibrium, the equilibrium
position will _______________ toward the direction that tends to minimize the stress. (Pure
_________________ and ________________ are not affected by changes in equilibrium.)
2. In chemistry, Le Chatlier’s Principle is used to manipulate the outcome of reversible reactions to
____________________ the amount of ________________ produced by altering the temperature,
pressure, or removing a reactant or product from a reaction.
3. An application of Le Chatlier’s Principle is ______________________________. This was used by
________________ in WWI to produce _________________ (NH3) for nitrogen containing
explosives. Today this process is used to create ammonia (_________) for household cleaners and
especially ________________ allowing for a four-fold increase in food production from 1900 to 2000.
4. There are _____ factors which determine whether a reaction favors making reactants
_____________________________ or favors making products ______________________________.
A. Changes in Concentration - (Reactants and Products)
1. Adding a substance to a system at equilibrium drives the system ______________ from that
substance and makes more of the substance(s) on the opposite side.
2. Removing a substance from a system at equilibrium drives the system toward _____________
that substance.
Ex) N2O4(g) ↔ 2NO2(g)
↑ N2O4(g) shift ____________ making more ___________
↑ NO2(g) shift ____________ making more ___________
↓ N2O4(g) shift ____________ making more ___________
↓ NO2(g) shift ____________ making more ___________
B. Changes in Pressure
1. Avogadro’s Law – Equal volumes of gases at the same temperature and pressure have the
__________ number of molecules. (1 mole of any gas at STP = _________ = 6.02 x1023
particles)
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2. According to Boyle’s Law an increase in pressure means a ________________ in volume. So
if the pressure is ____________________ on a system at equilibrium, the side which occupies
the _______________ volume will be favored. (inverse relationship)
3. If pressure is increased, the reaction will shift in the direction that produces __________ moles.
Ex)
2NO2(g) ↔
N2O4(g)
↑ pressure shift to _________ making more _______
2H2O2(g) ↔ 2H2O(g) + O2(g)
↑ pressure shift to _________ making more _______
H2(g) + Cl2(g) ↔ 2HCl(g)
↑ pressure shift to _________ making more _______
4. Pressure changes will only affect _____________.
C. Changes in Temperature
1. Exothermic Reactions __________________ heat. If temperature is increased on this system
then the reaction which absorbs or uses heat will ___________________. If temperature is
decreased on an exothermic reaction, then the reaction which releases heat will ____________
Ex) H2(g) + I2(g) ↔ 2HI(g) + Heat
Increasing the temperature will produce a higher yield of _______________.
Lowering the temperature will produce a higher yield of _______________.
2. Endothermic Reactions _________________ heat. If temperature is increased on this system
then the reaction which absorbs or uses heat will _____________. If temperature is decreased
on an endothermic reaction, then the reaction which absorbs heat will _________________.
Ex) Heat + NH4Cl(s) ↔ NH3(g) + HCl(g)
Increasing the temperature will produce a higher yield of _________________________.
Lowering the temperature will produce a higher yield of __________________________.
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Conclusion: These examples have been illustrations of ____________________ ___________________
which states that a system at ______________________, when subjected to a _____________, will
temporarily adjust itself to relieve the stress. This means that the ____________ to the right or left, or the
_____________________ forward or reverse reaction will be temporary and a new equilibrium will be
reestablished.
Practice:
1.
2SO2(g) +
O2(g)
 2SO3(g) + heat
What conditions of temperature and pressure favor high equilibrium concentrations of SO3?
(high / low) pressure; (high / low) temperature
2.
3H2(g)
+
N2(g)

2NH3(g)
+
heat
The commercial production of ammonia uses the Haber Process which is expressed by the above
equation. What condition of temperature and pressure will provide a maximum yield of NH3?
(high / low) pressure: (high / low) temperature
3.
4HCl(g)
+
O2(g)

2H2O(g) +
2Cl2(g) +
heat
Increasing the temperature of the reaction will (increase / decrease) the forward reaction.
Decreasing the pressure on the system will (increase / decrease) the forward reaction.
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