Monitoring and controlling chemical reactions Study Guide

A catalyst is a substance that increases the rate of a chemical reaction without being used up itself. This means that a small amount of catalyst can be used to process a large amount of reactants. Catalysts work by providing an alternative reaction pathway that has a lower activation energy. Activation energy is the minimum amount of energy required for reactants to transform into products. By lowering this energy barrier, more reactant particles possess the necessary energy to react upon collision, thus increasing the frequency of successful collisions. This ultimately leads to a faster rate of reaction. Important characteristics of catalysts include their specificity (some catalysts only work for particular reactions), their ability to be recovered chemically unchanged at the end of the reaction, and their susceptibility to poisoning by impurities, which can reduce their effectiveness. Catalysts do not change the yield of a reaction or the position of equilibrium; they only affect how quickly the equilibrium is reached or how quickly products are formed. For industries, catalysts are crucial as they allow reactions to proceed at lower temperatures and pressures, saving energy and reducing costs, making chemical processes more efficient and sustainable.

Many chemical reactions are reversible, meaning the products can react together to form the original reactants. When a reversible reaction takes place in a closed system, it eventually reaches a state of dynamic equilibrium. A closed system is one where no reactants or products can escape or be added; only energy can be exchanged with the surroundings. At dynamic equilibrium, the forward reaction (reactants forming products) continues to occur, and simultaneously, the reverse reaction (products forming reactants) also continues. The key characteristic of dynamic equilibrium is that the rate of the forward reaction and the rate of the reverse reaction become equal. This means that, although reactions are still happening, there is no net change in the concentrations of the reactants or products. The macroscopic properties of the system, such as colour, pressure, and concentration, remain constant over time because the rate of formation of products is exactly balanced by their rate of consumption, and vice versa for reactants. This balance makes the system appear static, but microscopically, continuous activity is occurring.