Coupled Reactions
Date Performed: November 26, 2010
Experiment No. 2 – Coupled Reactions
R.S. Velasco
Institute of Chemistry, College of Science
University of the Philippines, Diliman Quezon City, Philippines
Received Dec. 1, 2010
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ABSTRACT
The reaction of carbon dioxide gas to form carbon monoxide and oxygen gas is non-spontaneous (∆G > 0), thus we coupled it with the reaction that has a free energy that is negative enough to make the whole reaction spontaneous (∆G < 0). The second reaction involved magnesium ribbon. Two slabs of dry ice were set-up, with holes carved on both of them. When the magnesium ribbon was lighted on the first slab of ice, it produced a bright, white light, and was quickly covered with the second slab of dry ice. The reaction produced very bright light (which may cause blindness) and some sparks (exothermic reaction took place), which signified that the reaction between magnesium solid and carbon dioxide gas had been proceeding. The end result is solid magnesium oxide in the form of “white ball” and carbon solid in the form of coal. These products indicated that the coupling of the first two reactions was spontaneous with the theoretical value of ∆G= -372.2 kJ/mol.
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Introduction
Coupled reactions are very essential in our daily lives. One example of a coupled reaction is the metabolism of glucose (C6H12O6) that converts adenosine diphosphate (ADP) to adenosine triphosphate (ATP) in the mitochondria of cells. Coupling reactions is also used when extracting metals from their respective ores. As we can see, this way of making a certain reaction be spontaneous is a critical factor that can affect us in every little way. There are three ways to obtain product from a non-spontaneous reaction (∆G > 0): First, modify the different reaction conditions (usually, temperature) to
Experiment No. 2 – Coupled Reactions
R.S. Velasco
Institute of Chemistry, College of Science
University of the Philippines, Diliman Quezon City, Philippines
Received Dec. 1, 2010
-------------------------------------------------
-------------------------------------------------
ABSTRACT
The reaction of carbon dioxide gas to form carbon monoxide and oxygen gas is non-spontaneous (∆G > 0), thus we coupled it with the reaction that has a free energy that is negative enough to make the whole reaction spontaneous (∆G < 0). The second reaction involved magnesium ribbon. Two slabs of dry ice were set-up, with holes carved on both of them. When the magnesium ribbon was lighted on the first slab of ice, it produced a bright, white light, and was quickly covered with the second slab of dry ice. The reaction produced very bright light (which may cause blindness) and some sparks (exothermic reaction took place), which signified that the reaction between magnesium solid and carbon dioxide gas had been proceeding. The end result is solid magnesium oxide in the form of “white ball” and carbon solid in the form of coal. These products indicated that the coupling of the first two reactions was spontaneous with the theoretical value of ∆G= -372.2 kJ/mol.
-------------------------------------------------
Introduction
Coupled reactions are very essential in our daily lives. One example of a coupled reaction is the metabolism of glucose (C6H12O6) that converts adenosine diphosphate (ADP) to adenosine triphosphate (ATP) in the mitochondria of cells. Coupling reactions is also used when extracting metals from their respective ores. As we can see, this way of making a certain reaction be spontaneous is a critical factor that can affect us in every little way. There are three ways to obtain product from a non-spontaneous reaction (∆G > 0): First, modify the different reaction conditions (usually, temperature) to
References: [1] Petrucci, R.H., Harwood, W.S., Herring F.G. General Chemistry 8th ed. Prentince – Hall, Inc. New Jersey 1997. [2] http://www.chem.umn.edu