Physical chemistry Essay Example | Topics and Well Written Essays - 2000 words

Physical chemistry - Essay Example An understanding of the Le Chateliers principle and catalysis is essential for proceeding with this study. Increase in temperature: Exothermic reaction favours reactants, as the heat is absorbed to counterbalance the increase in temperature. Endothermic reaction favours products as the absorbed heat facilitates a larger amount of reactants to convert to products (Atkins & de Paula, 2006). Change in reactant concentration: An increase in concentration of a reactant in a dynamic equilibrium causes the reaction to favour products, as the excess reactant reacts with other reactants. A decrease in concentration of a reactant favours the reverse reaction as the products are converted to reactants in order to balance the decrease in reactant concentration. (Clark, 2002; Morrison & Boyd, 1992) Change in product concentration: A decrease in product concentration favours the forward reaction to balance the decrease. An increase in product concentration favours the reverse reaction. (Atkins & de Paula, 2006) Change in pressure: Increasing the pressure of a system at equilibrium causes changes in the partial pressures of reactants and products. The rate constant is independent of the change in pressure of a system, but depends on ratio of partial pressures of the reactants and products. The reaction moves in the direction where number of moles is less. (Atkins & de Paula, 2006) A catalyst accelerates a chemical reaction without undergoing a net chemical change. The catalyst reduces the energy of activation by altering the path of reaction to avoid the rate determining step, which is the slowest step in a reaction (Atkins & de Paula, 2006). For example, decomposition of hydrogen peroxide, which is a slow reaction at room temperature, requires activation energy of 76 kJ/mol. In the presence of iodide ions, this activation energy drops to 57 kJ/mol and rate constant