Chemistry Experiment
EXPERIMENT NO. 4
Chemical Equilibrium
Claver, L. Z. X. Y.1, Palad, C. C.2, Rocha, R. D. P3
1Anthropology Department, College of Social Sciences and Philosophy, 2National Institute of Geological Sciences, College of Science, 3Department of Food Science and Nutrition, College of Home Economics,
University of the Philippines, Diliman, Quezon City 1101 Philippines
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Keywords: forward and reverse reactions, equilibrium constant, Le Chatelier’s Principle, reaction quotient
Introduction
In chemical kinetics, it is stated that a forward reaction’s rate is dependent on the given concentration of the reactants. In other words, the relationship of the rate of a reaction is directly proportional to the concentration. While the reaction is taking place, the concentration of the reactants are decreased, as these reactants are formed into products. During the decrease of the reactants’ concentration, the rate of the forward reaction also decreases. As more and more products are being formed, they start to reform to their constituent reactants again. This causes the reverse reaction rate to increase this time. This process continues to happen until the rate of the forward reaction and the backward reaction becomes equal. When this happens, chemical equilibrium is achieved by the reaction system. Whenever equilibrium is achieved, at any given time, both reactants and products will be present at any given point in time since their concentrations remain constant. Given a reaction,
aA + bB ⇌ cC + dD
kf[A]a[B]b = kr[C]c[D]d
kfkr = Keq = [C]c[D]d (1) [A]a[B]b
A factor in determining whether to which direction a reaction will go to that has not yet reached equilibrium, is the reaction quotient Q. Q is just the same as the Keq expression, but the main difference is that the concentrations of the reactants and the products used in the equation are still not yet at equilibrium. Whenever Q<Keq,
Chemical Equilibrium
Claver, L. Z. X. Y.1, Palad, C. C.2, Rocha, R. D. P3
1Anthropology Department, College of Social Sciences and Philosophy, 2National Institute of Geological Sciences, College of Science, 3Department of Food Science and Nutrition, College of Home Economics,
University of the Philippines, Diliman, Quezon City 1101 Philippines
-------------------------------------------------
Keywords: forward and reverse reactions, equilibrium constant, Le Chatelier’s Principle, reaction quotient
Introduction
In chemical kinetics, it is stated that a forward reaction’s rate is dependent on the given concentration of the reactants. In other words, the relationship of the rate of a reaction is directly proportional to the concentration. While the reaction is taking place, the concentration of the reactants are decreased, as these reactants are formed into products. During the decrease of the reactants’ concentration, the rate of the forward reaction also decreases. As more and more products are being formed, they start to reform to their constituent reactants again. This causes the reverse reaction rate to increase this time. This process continues to happen until the rate of the forward reaction and the backward reaction becomes equal. When this happens, chemical equilibrium is achieved by the reaction system. Whenever equilibrium is achieved, at any given time, both reactants and products will be present at any given point in time since their concentrations remain constant. Given a reaction,
aA + bB ⇌ cC + dD
kf[A]a[B]b = kr[C]c[D]d
kfkr = Keq = [C]c[D]d (1) [A]a[B]b
A factor in determining whether to which direction a reaction will go to that has not yet reached equilibrium, is the reaction quotient Q. Q is just the same as the Keq expression, but the main difference is that the concentrations of the reactants and the products used in the equation are still not yet at equilibrium. Whenever Q<Keq,
References: Petrucci, Ralph H.,William S. Harwood, and Geoffrey F. Herring (2002). 8th edition. Masterton, William L. Cecile N. Hurley, and Edward J. Neth (2011). 7th edition. Chemistry: Principles and Reactions. CENGAGE Learning. Equilibrium Constants. http://www.ausetute.com.au/equicons.html Retrieved last: April 24, 2012. Appendix K2K1’ = K = (9.77x1012)(37) K = [Cr2O72-] = 3.61x1014