Melting Point and Recrystallization
Recrystallization and Melting Point of Benzoic Acid
Organic Chemistry 1
10/4/12
Abstract Recrystallization was done to remove impurities from the sample. The percent recovery of benzoic acid during recrystallization is 23.02%. The difference between the pure and impure samples was observed by comparison of melting points. It was found that impure sample had a lower and wider melting point range of 120.1-122.2 (C). The pure sample melting point range was 121.3-122.5 (C). These ranges helped determine purity by comparing the known melting point of pure benzoic acid.
Introduction
Most of the organic substances recovered from organic reactions are impure and require purification to obtain the desired pure product. The extracted benzoic acid still had impurities which can be removed through the process of recrystallization. Recrystallization is a purification technique that relies on the differing solubility of compounds within a mixture separating to form a pure crystalline solid of the desired product. Often the desired compound is present in a larger quantity within the solution. Therefore, a pure sample of this compound can be crystallized from the solution while leaving the impurities dissolved within the solvent. Recrystallization is highly dependent upon the solubility of the two mixed compounds. Solubility is the property of how well a solute dissolves in a solvent. Solubility increases with an increase in energy within the system. This is due to the increased kinetic energy of the molecules leading to more collisions of the solvent with the solute. This process is called dissociation since the molecules of the solute become separated and surrounded by molecules of solvent. Solvation occurs once the lattice has completely dissociated within the solution and no traces of solid compound remain. These steps can be explained by Gibb’s Free Energy (∆G) equation where a negative ∆G indicates a spontaneous reaction. The solvation of the lattice structure is a
Organic Chemistry 1
10/4/12
Abstract Recrystallization was done to remove impurities from the sample. The percent recovery of benzoic acid during recrystallization is 23.02%. The difference between the pure and impure samples was observed by comparison of melting points. It was found that impure sample had a lower and wider melting point range of 120.1-122.2 (C). The pure sample melting point range was 121.3-122.5 (C). These ranges helped determine purity by comparing the known melting point of pure benzoic acid.
Introduction
Most of the organic substances recovered from organic reactions are impure and require purification to obtain the desired pure product. The extracted benzoic acid still had impurities which can be removed through the process of recrystallization. Recrystallization is a purification technique that relies on the differing solubility of compounds within a mixture separating to form a pure crystalline solid of the desired product. Often the desired compound is present in a larger quantity within the solution. Therefore, a pure sample of this compound can be crystallized from the solution while leaving the impurities dissolved within the solvent. Recrystallization is highly dependent upon the solubility of the two mixed compounds. Solubility is the property of how well a solute dissolves in a solvent. Solubility increases with an increase in energy within the system. This is due to the increased kinetic energy of the molecules leading to more collisions of the solvent with the solute. This process is called dissociation since the molecules of the solute become separated and surrounded by molecules of solvent. Solvation occurs once the lattice has completely dissociated within the solution and no traces of solid compound remain. These steps can be explained by Gibb’s Free Energy (∆G) equation where a negative ∆G indicates a spontaneous reaction. The solvation of the lattice structure is a
References: 1. Methyl Orange MSDS; CAS#: 547-58-0 2, Benzoic Acid MSDS; CAS# 65-85-0 [Online]; Sciencelab.com, Inc.: Houston, Texas, June 9, 2012. http://www.sciencelab.com/msds.phpmsdsld=9927096 (Accessed September 11, 2012) 2. Padías, A. (2011). Making the Connections2 A How-To Guide for Organic Chemistry Lab Techniques. 2ed. The University of Arizona. Plymouth: Hayden-McNeil Publishing, LLC.