Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
Related questions
Question
Write the mass action expression for Kc, the equilibrium constant
![6:22
kud21.kutztown.edu
1 of 4
Observations will be made and chemical formulas will be predicted for the ions present in
solution. Three separate systems will be studied: Acid-Base Indicator, Complex lon, and
Gas Phase Equilibria.
Theory
Before focusing on specific examples, first consider the general reaction:
A(aq) B(aq) + C(aq)
(1)
where A, B, and C are molecules or ions in solution. If these species are in equilibrium, their
concentrations are related by an equilibrium constant, Kc, for the reaction at a given
temperature. The mass action expression for the general reaction above is as follows:
[B][C]
[Alq
=K₂
.5G
− +
-
(2)
and can be used to calculate Kc from the equilibrium concentrations of the reactants and
products. The subscript eq refers to the concentration of a reactant or product at
equilibrium. Equilibrium, not initial, concentrations are used to compute Ke. If a change
occurs i one of the reactant or product concentration, then changes in equilibrium
concentrations of all the components will occur. For example, what if the concentration of
A decreases? Remember, K, is a constant (at a specific temperature)!
Materials
If [A] has decreased, the reaction equilibrium must shift to the left to replenish the missing
A so that the ratio of products to reactants remains the same as it was before the
disturbance.
A(aq) B(aq) + C(aq)
If then rxn shifts ←
6.0 M HCI
Consider another situation where the concentration of A is increased. The ratio of products
to reactants, as calculated in Eq. 2, would change to keep K, constant. In order to determine
the directionality of the shift that would need to occur, we need to determine what
equilibrium concentrations would cause Kc to attain the value it had before the disturbance.
(i.e. Does the concentration of reactants or products need to increase to account for the
change in concentration?)
This analysis of how the equilibrium shifts as the system is disturbed can be summarized by
Le Chatelier's Principle, which states:
When a system that is in dynamic equilibrium is subjected to a disturbance that upsets the
equilibrium, the system undergoes a change that counteracts the disturbance and, if
possible, restores equilibrium.¹
In addition to changes in concentration, a system in equilibrium can also be disturbed by
changes in pressure or volume (gas systems) with no change to the equilibrium constant.
Temperature changes can also disturb the equilibrium of a system (exothermic vs.
endothermic) but unlike with the other disturbances, the value of Kc changes with
temperature. The following experiments will look more closely at specific disturbances of
systems in equilibrium.
12.01CH
2
cobalt(II) chloride](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F6458f460-a493-4a03-9ae9-5e56c703a871%2F2b83859e-cd82-423c-b0e1-5b136c29ef82%2F56z7ku_processed.jpeg&w=3840&q=75)
Transcribed Image Text:6:22
kud21.kutztown.edu
1 of 4
Observations will be made and chemical formulas will be predicted for the ions present in
solution. Three separate systems will be studied: Acid-Base Indicator, Complex lon, and
Gas Phase Equilibria.
Theory
Before focusing on specific examples, first consider the general reaction:
A(aq) B(aq) + C(aq)
(1)
where A, B, and C are molecules or ions in solution. If these species are in equilibrium, their
concentrations are related by an equilibrium constant, Kc, for the reaction at a given
temperature. The mass action expression for the general reaction above is as follows:
[B][C]
[Alq
=K₂
.5G
− +
-
(2)
and can be used to calculate Kc from the equilibrium concentrations of the reactants and
products. The subscript eq refers to the concentration of a reactant or product at
equilibrium. Equilibrium, not initial, concentrations are used to compute Ke. If a change
occurs i one of the reactant or product concentration, then changes in equilibrium
concentrations of all the components will occur. For example, what if the concentration of
A decreases? Remember, K, is a constant (at a specific temperature)!
Materials
If [A] has decreased, the reaction equilibrium must shift to the left to replenish the missing
A so that the ratio of products to reactants remains the same as it was before the
disturbance.
A(aq) B(aq) + C(aq)
If then rxn shifts ←
6.0 M HCI
Consider another situation where the concentration of A is increased. The ratio of products
to reactants, as calculated in Eq. 2, would change to keep K, constant. In order to determine
the directionality of the shift that would need to occur, we need to determine what
equilibrium concentrations would cause Kc to attain the value it had before the disturbance.
(i.e. Does the concentration of reactants or products need to increase to account for the
change in concentration?)
This analysis of how the equilibrium shifts as the system is disturbed can be summarized by
Le Chatelier's Principle, which states:
When a system that is in dynamic equilibrium is subjected to a disturbance that upsets the
equilibrium, the system undergoes a change that counteracts the disturbance and, if
possible, restores equilibrium.¹
In addition to changes in concentration, a system in equilibrium can also be disturbed by
changes in pressure or volume (gas systems) with no change to the equilibrium constant.
Temperature changes can also disturb the equilibrium of a system (exothermic vs.
endothermic) but unlike with the other disturbances, the value of Kc changes with
temperature. The following experiments will look more closely at specific disturbances of
systems in equilibrium.
12.01CH
2
cobalt(II) chloride
Expert Solution
Step 1
Given that,
Chemical reaction,
A(aq) <------> B(aq)+C(aq)
We have to write the mass action expression for Kc, the equilibrium constant.
Step by step
Solved in 2 steps
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