Application of Le Chatelier's Principle
Le Chatelier's Principle is a concept in chemistry that predicts how a system at equilibrium will respond to changes in concentration, pressure, or temperature. It states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore equilibrium. This principle is widely used to understand and predict the behavior of chemical reactions in various applications.
4 Key excerpts on "Application of Le Chatelier's Principle"
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...This is known as Le Chatelier's principle, after the nineteenth century chemist Henry-Louis Le Chatelier, who studied the effects of changes in reaction conditions on a chemical equilibrium. The exact statement of Le Chatelier's principle is; • When a chemical reaction at equilibrium is subjected to a change in reaction conditions, the position of the equilibrium will shift to counteract the effect of the change until a new equilibrium is established. The ways that a chemical reaction at equilibrium will respond when disturbed by a change in the original conditions can be predicted. These predicted responses and their effects on the equilibrium constant are summarized in Table 7.1 for each of the changing conditions. If the concentration of a reactant or product in a reversible chemical reaction at equilibrium is changed, by the addition or the removal of either a reactant or a product, the equilibrium will be reestablished by adjusting the concentrations of reactants and products so that their ratio and the value of K eq will remain the same. For example, if the concentration of reactant A in the generic Eq. (3) of Section 7.1 is increased by the addition of A to the reaction system, the reaction will shift to consume the added reactant A and form more of the products C and D. This increases the value of the numerator of K eq and decreases the value of the denominator compensating for the increase in the value of the denominator caused by the added reactant. This response can be useful in an industrial process if it is necessary to convert the maximum possible amount of reactant B into the products C and D when reactant B is an expensive or rare material and reactant A is inexpensive and abundant. In this case, the addition of excess reactant A becomes a means of conserving the more expensive reactant B while producing as much product as possible...
eBook - ePubChemistry
Concepts and Problems, A Self-Teaching Guide
- Richard Post, Chad Snyder, Clifford C. Houk(Authors)
- 2020(Publication Date)
- Jossey-Bass(Publisher)
...Such stresses as adding more of a reactant or product to a reaction, or changing the pressure of a reaction involving gases, will have effects that can be predicted through Le Chatelier's Principle. Le Chatelier's Principle states that when a stress is placed on an equilibrium system, the equilibrium will shift so that the stress is (increased, relieved) __________. Answer: relieved The following reaction can serve as an example of what happens when a stress is placed upon a chemical equilibrium. First, write the equilibrium constant expression for this reaction. K eq = _____________ Answer: Assume that at a certain temperature, the concentration in mol/liter of each equilibrant in the reaction from frame 32 is as follows. Calculate the value of K eq __________ Answer: To observe the effects of Le Chatelier's Principle, we now add an additional 6 mol/liter of Cl 2 gas to the equilibrium. We suddenly have a total of 12 mol/liter of Cl 2 as well as the original amount of PCl 3 and PCl 5. The system is no longer at equilibrium. Immediately, one of the reaction rates (forward or reverse) increases so as to relieve the stress. Look carefully at the reversible reaction. Since the concentration of Cl 2 has just doubled, the reaction will try to relieve that stress. As a response to all that extra Cl 2, which of the following would you expect to happen? The forward reaction rate increases (producing even more Cl 2 and PCl 3 while reducing the PCl 5). The reverse reaction increases (reducing the supply of Cl 2 and PCl 3 while increasing the PCl 5). ____________ Answer: (b) (This is logical since there is a surplus of Cl 2...
eBook - ePub- Kevin R. Reel(Author)
- 2013(Publication Date)
- Research & Education Association(Publisher)
...CHAPTER 6 Equilibrium CHAPTER 6 EQUILIBRIUM LE CHATELIER’S PRINCIPLE • Le Chatelier’s principle states that when a system at equilibrium is disturbed by a change in pressure, temperature, or the amount (concentration) of product or reactant, the reaction will shift to minimize the change and establish a new equilibrium. • Change in concentration: Adding products to a reaction the equilibrium will shift the reaction to produce reactants; adding reactants to a reaction at equilibrium will shift the reaction to produce products. See the section on the reaction quotient, Q, below. • Change in temperature: An increase in temperature causes the equilibrium to shift to use up the added heat. For example, when heat is added to an exothermic reaction, it will shift to the left to use up the heat. An endothermic reaction will shift to the right to use up heat when heat is added. • Change in pressure: An increase in pressure causes the equilibrium to shift in the direction that produces the fewest number of gas moles. For example, in the reaction that dissolves a gas into a liquid, increasing the pressure on the system will cause the equilibrium to shift to produce more dissolved gas. • Addition of a catalyst or an inert gas will not cause the equilibrium to shift; the amounts of reactants and products would remain unchanged. EQUILIBRIUM CONSTANTS • Equilibrium constants are ratios. For the reaction, aA + bB ↔ cC + dD, The ratio of the product concentrations, raised to their stoichiometric coefficients, to the reactant concentrations, raised to their stoichiometric coefficients, is the equilibrium constant, K eq...
eBook - ePubMWH's Water Treatment
Principles and Design
- John C. Crittenden, R. Rhodes Trussell, David W. Hand, Kerry J. Howe, George Tchobanoglous(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
...In other words, reactions such as that shown in Eq. 5.3 will not usually achieve complete conversion of reactants to products but instead will reach a state of dynamic equilibrium. Dynamic equilibrium is characterized by a balance between the continuous formation of products from reactants and reactants from products. If there is a change or stress to the system that affects the balance, the amount of reactants and products present will change to accommodate the stress. This concept is known as Le Chatelier's principle, which states that a reaction at equilibrium shifts in the direction that reduces a stress to the reaction. For example, in Eq. 5.21 if constituent A is removed from the system, the equilibrium will shift to form more A. In a chemical system, the difference between the actual state and the equilibrium state is the driving force used to accomplish treatment objectives. Equilibrium Constants When chemical reactions come to a state of equilibrium, the numerical value of the ratio of the concentration of the products over the concentration of the reactants all raised to the power of the corresponding stoichiometric coefficients is known as the equilibrium constant (K c) and, for the reaction shown in Eq. 5.21, is written as 5.32 where K c = equilibrium constant (subscript c used to signify equilibrium constant based on species concentration) [ ] = concentration of species, mol/L a, b, c, d = stoichiometric coefficients of species A, B, C, D, respectively For example, the ionization of carbonic acid, given previously as Eq...
