Reaction Rate 2023 with verified questions and answers

reaction rate The change in concentration of a reactant or product per unit time collision theory atoms, ions, and molecules can react to form products when they collide, provided that the particles have enough kinetic energy Factors that affect reaction rate nature of the reactants, concentration, pressure of gases, temperature, surface area and the presence of a catalyst Nature of the reactants small molecules with fewer bonds, ionic bonds, single bonds will react faster Surface area As you increase the surface area you provide more space for effective collisions. Effective collision A collision in which the particles meet with sufficient energy ( greater than the activation energy) and an orientation that allows them to react. Temperature Increasing the temperature of a system speeds up the particles and gives them more opportunities for effective collisions to occur. Pressure Increasing the pressure of a system will speed up the rate of reaction for gases only. Since gas particles are spread out, increasing the pressure forces the particles closer together making it easier for there to be effective collisions open system A system in which both energy and matter are exchanged with the surroundings. closed system A system in which no matter is allowed to enter or leave concentration Increasing the concentration supplies more moles per liter of solution. Since the volume is not changing, there are more particles in the solution which means that there are more chances for effective collisions. catalyst (chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected activation energy The amount of energy needed for a reaction to occur. This is needed to form the activated complex which will lead to product formation. endothermic reaction A reaction that ABSORBS energy in the form of heat. The products have more potential energy than the reactants as a result. exothermic reaction A reaction that RELEASES energy in the form of heat. The reactants have more potential energy than the products. reaction progress curve Shows the change in energy of particles throughout a chemical reaction activated complex a high energy transitional structure in a chemical reaction where old bonds are breaking and new bonds are forming intermediate A substance formed during a chemical process before the desired product is obtained which is stable enough to be observed reaction mechanism the step-by-step sequence of reactions which explain how the reactant atoms rearranged to form the products rate law expression Mathematical expression describing how the rate of a reaction will vary with concentration of reactants, determined experimentally, R = k [reactants] elementary step name used to describe each step in the process of converting reactants to products rate determining step slowest step; determines the rate of the reaction; only dependent upon concentration of the reactants involved in the rate-determining step first order reaction a reaction in which the reaction rate is proportional to the concentration of only one reactant second order reaction a reaction whose rate depends on the concentration of one reactant raised to the second power or on the concentrations of two different reactants, each raised to the first power third order reaction The rate is proportional to the cube of the concentration. overall order of the reaction sum of the exponents of the concentrations in the rate law expression shape of a reaction progress curve A reaction which occurs without an intermediate will have a single activation energy and will have one "bump" along the way. For each additional step there will be another activation energy. The valley between the "bumps" represents the presence of an intermediate. homogeneous system one in which the reactants and products are present in the same phase and will react more rapidly than if there were mixed phases. Solids will react slower than gas systems. heterogeneous system one in which the reactants and products are present in more than one phase.