8.4 Concentration and the rate of reaction

• Biological catalysts: Substances, typically proteins or RNA molecules, that accelerate chemical reactions within living organisms by lowering the activation energy required for the reactions to occur, thereby increasing the rate of the reactions without being consumed in the process.
• Catalase: An enzyme found in living cells, particularly in the liver and other tissues, that catalyzes the decomposition of hydrogen peroxide into water and oxygen. This reaction helps to protect cells from damage caused by the buildup of hydrogen peroxide, a toxic byproduct of metabolism.
• Catalyst: A substance that speeds up the rate of a chemical reaction by providing an alternative reaction pathway with lower activation energy, thus increasing the rate of reaction without being consumed or permanently altered in the process.
• Decompose: To break down or disintegrate into simpler substances through chemical reactions or processes.
• Enzymes: Protein molecules that act as biological catalysts, facilitating and speeding up chemical reactions within living organisms by lowering the activation energy required for the reactions to proceed. Enzymes are highly specific, typically catalyzing specific biochemical reactions, and they remain unchanged after the reaction.
• Concentration Effect: Higher concentrations of hydrochloric acid result in more frequent collisions between hydrochloric acid particles and calcium carbonate particles, leading to faster reaction rates.
• Catalysts: Catalysts are substances that accelerate chemical reactions without being consumed in the process. They provide an alternative reaction pathway with lower activation energy, thereby increasing the rate of reaction. Catalysts are cost-effective alternatives to increasing temperature, concentration, or surface area in industrial processes, as they can be reused and do not require additional energy or resources. For example, catalytic converters in car exhaust systems contain catalysts that accelerate the conversion of harmful gases into less harmful substances, improving air quality.
• 1. Biological Catalysts (Enzymes): Enzymes are biological catalysts found in living organisms that speed up biochemical reactions. For example, the enzyme catalase helps in the breakdown of hydrogen peroxide into water and oxygen, preventing cellular damage. Enzymes are essential for various physiological processes, including digestion, where they facilitate the breakdown of food molecules. Some cleaning products, known as biological washing powders, contain enzymes that aid in removing stains such as food and blood.
• Concentration refers to the amount of a substance (reactant or product) present in a given volume or space. In the context of chemical reactions, it specifically relates to the amount of reactant molecules per unit volume.
• What:Concentration affects the rate of a chemical reaction. When the concentration of reactants increases, the rate of reaction typically increases as well. This relationship is governed by the collision theory, which states that reactions occur when reactant molecules collide with sufficient energy and proper orientation.
• Why:Higher concentrations mean a greater number of reactant particles per unit volume. With more particles in close proximity, the frequency of collisions between reactant molecules increases. This leads to more effective collisions, where molecules collide with enough energy to overcome the activation energy barrier and undergo a reaction. As a result, the rate of reaction increases.
• When:The effect of concentration on the rate of reaction is observed throughout the entire reaction process. However, the impact may be more pronounced during the initial stages of the reaction when there are more reactant molecules available for collision.
• How:Increasing the concentration of reactants increases the likelihood of collision between reactant particles. This results in a higher frequency of collisions with sufficient energy to initiate the reaction, ultimately leading to an increase in the rate of reaction. Conversely, decreasing the concentration of reactants reduces the number of collisions, resulting in a slower reaction rate.