General Chemistry Thermal Analysis Lab

General Chemistry Thermal Analysis Lab - Thermal Stability...

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Thermal Stability Analysis of [Co(NH 3 ) 5 Cl]Cl 2 Introduction This experiment was performed in order to determine the thermal stability of the compound [Co(NH 3 ) 5 Cl]Cl 2 , and whether or not it can survive in aqueous solution at temperatures up to 80 degrees Celsius for 90 minutes. Quantitative analysis was done with respect to the rate and activation energy of the reaction at different temperatures from 60-80 degrees Celsius to discover how well the compound could survive in aqueous solution. Because this compound’s adhesive formulation contained an adhesive stabilizer, the concentration of acid HNO 3 was also set as a variable. The balanced chemical equation is shown below: [Co(NH 3 ) 5 Cl] 2+ (heat) [Co(NH 3 ) 5 (H 2 O)] 3+ + Cl - The rate of the reaction signifies the rate at which reactants are converted to products. In this particular reaction, the rate was influenced by various factors including concentrations of the reactants, temperature at which the reaction occurred, and whether or not a catalyst was present. In this reaction, the rate was directly proportional to the concentration of the reactants. Therefore, if the concentration of reactants decreased by a factor of 2, the reaction rate would decrease by a factor of 2. This particular reaction is considered first-order and its rate only changes with respect to the concentration of [Co(NH 3 ) 5 Cl] 2+ . The equation, or rate law, for the reaction is shown below: Rate = k[Co(NH 3 ) 5 Cl] 2+ The exponent on the concentration of the reactant in the rate equation is 1, which explained why each concentration was directly proportional to the rate. However, the reason why this was true requires an understanding of the collision model for the reaction, the orientation factor, and the number of molecules that are considered to have a minimum activation energy. The collision model states that molecules cannot react unless they come into contact with each other. Therefore, the reaction rate decreases when less molecules occupy the same space, which is what happens when the concentration is smaller. Because there are fewer molecules available to collide with each other, the probability for a collision is less as well. Sometimes, however, molecules that collide do not react with each other. This is due to the orientations of the molecules, called the orientation factor, and the activation energy barrier. For molecules to react, in addition to the collision taking place, each
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molecule must be orientated in the correct atomic spatial configuration at the time of collision. In fact, only a small portion of molecules are generally oriented in a way suitable for a reaction to occur. The other factor required for a reaction to occur is sufficient activation energy, meaning that a molecule must hold at least a designated minimum energy. In any reaction, it takes a considerable amount of energy to change the structure of the reactant and convert it into the product. This point at which reactants change to products
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General Chemistry Thermal Analysis Lab - Thermal Stability...

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