Investigating Chemical Equilibrium
Date: 30th April 2013
Due Date: 15th May 2013
Prepared For: M. Seraji
Prepared by: Andrea Odunze
Many reactions proceed to a state of equilibrium. A chemical reaction at equilibrium, where the rates of the forward reaction and reverse reaction are equal, looks like this: A + B AB
There are three factors, according to Le Chatelier’s principle, that affect the equilibrium position and equilibrium constant. These are the concentrations of products and reactants, changes in temperature and gas volume. When influenced by these factors, the chemical system has to experience an equilibrium shift, a change in concentrations of the products (shift to the right) or a change in concentrations of the reactants (shift to the left) in order to achieve equilibrium. The purpose of this experiment was to interpret and further understand the effect of these factors on a chemical equilibrium using Le Chatelier’s principle.
Equilibrium is a state of physical balance ("Equilibrium”). A chemical system in a state of equilibrium means that both reactants and products exist together in the system and there is a balance of external influences on the system. This is as a result of some of the product molecules formed in the forward reaction having enough energy to convert back to reactants in a reverse reaction. The conditions required for a chemical system to be at a chemical equilibrium are; the reaction has to happen in a closed system, the concentrations of both reactants and products should be constant and microscopic variables such as temperature and pressure have to be constant (DiGiuseppe 420).
In a chemical equilibrium, the point where the concentrations of the products and reactants are constant is called the equilibrium position. This can be mathematically described in an equilibrium law. It is further defined in the equation by a value called the equilibrium constant, Kc (DiGiuseppe 421). Kc = [products]/ [reactants]
“When a chemical system at equilibrium is disturbed by a change in a property, the system adjusts in a way that opposes it” (DiGiuseppe). This is Le Chatelier’s principle and it states that chemical systems shift to restore their state of equilibrium when disrupted by external factors. These factors are the concentration of the products and reactants in the reaction, any changes in temperature and changes in gas volume. (DiGiuseppe 439). According to Le Chatelier’s Principle, systems oppose the three different factors that affect equilibrium by responding in the following ways: Concentration: Increasing the concentration of products will increase the available products that are reforming into reactants so the system responds by shifting to the left, towards the reactant side for equilibrium to be achieved. Increasing the concentration of reactants will increase the available reactants that are making products so the system responds by shifting to the right, towards the reactant side for equilibrium to be achieved. Temperature: Reactions are described as exothermic or endothermic. Exothermic reactions are reactions where the potential energy of products is less than the potential energy of reactants resulting in a release of energy and a negative enthalpy (∆H) value. In a chemical equation, this value is written as a positive value on the product side. Increasing the temperature of this type of reaction makes more products available to reform into reactants; therefore, the system responds by a shift to the left, towards the reactant side for equilibrium to be achieved. Endothermic reactions are reactions where the potential energy of products is greater than the potential energy of reactants due to absorption of energy and a positive enthalpy (∆H) value. In a chemical equation, this value is written as a positive value on the reactant side. Increasing the temperature of this type of reaction makes more reactants available to form...
Cited: "Anesthesiologist." Dictionary.com. Dictionary.com, n.d. Web. 12 May 2013
"Bicarbonate Buffering System." Wikipedia. Wikimedia Foundation, 05 Oct. 2013. Web. 14 May 2013.
DiGiuseppe, Maurice. Chemistry 12. Toronto: Nelson Education, 2011. 286. Print
"Equilibrium." Dictionary.com. Dictionary.com, n.d. Web. 12 May 2013.
Mustoe, Frank J. "Reversible Reactions and Chemical Equilibrium." McGraw-Hill Ryerson
Chemistry 12. Toronto: McGraw-Hill Ryerson, 2002. 322-72. Print.
Please join StudyMode to read the full document