1. Chapter 13 Reaction Rates and Chemical Equilibrium
Learning Goal Use the concept of reversible reactions to explain chemical equilibrium.
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2. As the reactants SO2 and O2 collide, the forward reaction begins.
Reversible Reactions
As the reactants SO2 and O2 collide, the forward reaction begins.
2SO2(g) + O2(g) SO3 (g)
SO3 molecules begin to form and collide with each other to form reactants in the reverse reaction. This reversible reaction is written with a double arrow forward
2SO2(g) + O2(g) SO3(g)
reverse
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3. occurs in both the forward and reverse direction forward
Reversible Reactions
A reversible reaction
occurs in both the forward and reverse direction
forward
2SO2(g) + O2(g) SO3(g)
reverse
has two rates, a rate for the forward reaction and a rate for the reverse reaction
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4. Write the forward and reverse reactions for the following:
Learning Check
Write the forward and reverse reactions for
the following:
CH4(g) + 2H2S(g) CS2(g) + 4H2(g)
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5. Write the forward and reverse reactions for the following:
Learning Check
Write the forward and reverse reactions for
the following:
CH4(g) + 2H2S(g) CS2(g) + 4H2(g)
The forward reaction is:
The reverse reaction is:
CS2(g) + 4H2(g) CH4(g) + 2H2S(g)
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6. A reaction reaches chemical equilibrium when
no further changes take place in the concentration
of the reactants and products.
At equilibrium,
the rate of the forward reaction is equal to the rate of the reverse reaction
the forward and reverse reactions continue at the same rate
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7. Chemical Equilibrium
As a reaction progresses, the rate of the forward reaction decreases and that of the reverse reaction increases until they become equal.
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8. Chemical Equilibrium
Equilibrium is reached when there is no further change in the concentrations of the reactants and products.
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9. For the reaction at equilibrium H2(g) + I2(g) 2HI(g)
the forward reaction is H2(g) + I2(g)  2HI(g)
the reverse reaction is 2HI(g)  H2(g) + I2(g)
the amounts of H2, I2, and HI are constant
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10. Reaction Rates at Equilibrium
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11. Complete each of the following with equal or not
Learning Check
Complete each of the following with equal or not
equal, change or do not change.
Before equilibrium is reached, the concentrations of the reactants and products_______.
At equilibrium, the rate of the forward reaction is ______to the rate of the reverse reaction.
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12. Complete each of the following with equal or not
Solution
Complete each of the following with equal or not
equal, change or do not change.
Before equilibrium is reached, the concentrations of the reactants and products change.
At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.
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13. Forward and Reverse Reactions
Given the reaction:
2SO2(g) + O2(g) SO3(g)
starting with the reactants, SO2 and O2, the product SO3 is formed until equilibrium is reached
starting with only the product SO3, the reaction forms SO2 and O2 until equilibrium is reached
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14. Forward and Reverse Reactions
The equilibrium concentrations of SO2, O2, and SO3 are the same for both the forward and reverse reactions.
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15. Complete each sentence with (1) equal (2) not equal (3) forward
Learning Check
Complete each sentence with
(1) equal (2) not equal (3) forward
(4) reverse (5) changes (6) does not change
A. Reactants form products in the ________ reaction.
B. At equilibrium, the reactant concentration _______.
C. When products form reactants, it is the _______ reaction.
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16. Complete each sentence with (1) equal (2) not equal (3) forward
Solution
Complete each sentence with
(1) equal (2) not equal (3) forward
(4) reverse (5) changes (6) does not change
A. Reactants form products in the (3) forward reaction.
B. At equilibrium, the reactant concentration (6) does not change.
C. When products form reactants, it is the (4) reverse reaction.
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17. Complete each sentence with (1) equal (2) not equal (3) forward
Learning Check
Complete each sentence with
(1) equal (2) not equal (3) forward
(4) reverse (5) changes (6) does not change
At equilibrium, the rate of the forward reaction is ______ to the rate of the reverse reaction.
B. If the forward reaction is faster than the reverse, the amount of products ______.
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18. Complete each sentence with (1) equal (2) not equal (3) forward
Learning Check
Complete each sentence with
(1) equal (2) not equal (3) forward
(4) reverse (5) changes (6) does not change
At equilibrium, the rate of the forward reaction is (1) equal to the rate of the reverse reaction.
B. If the forward reaction is faster than the reverse, the amount of products (5) changes.
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