Chapter 4: rates of reactions Flashcards
What factors affect the rate and yield of chemical reactions?
Factors include temperature, surface area, concentration, gas pressures, presence of a catalyst, activation energy, and orientation.
Define Le Chatelier’s principle.
Le Chatelier’s principle explains how a system at equilibrium responds to changes in conditions by shifting to counteract those changes and restore equilibrium.
What is the collision theory?
The collision theory explains that for a chemical reaction to occur, reactant particles must collide with sufficient energy and in the correct orientation to break the bonds between them and form new products.
How does surface area affect the rate of a chemical reaction?
Increasing the surface area of a solid or liquid reactant increases the number of exposed particles available for reaction, thus increasing the rate of reaction.
Explain how concentration affects the rate of a chemical reaction.
Higher concentrations of reactants lead to more frequent collisions between particles, increasing the rate of reaction.
What role does temperature play in the rate of a chemical reaction?
Higher temperatures increase the average kinetic energy of particles, leading to more collisions with sufficient energy to overcome the activation energy barrier and thus increase the reaction rate.
How do catalysts affect the rate of a chemical reaction?
Catalysts decrease the activation energy required for a reaction, providing an alternative pathway for the reaction to proceed faster without being consumed themselves.
Define open and closed systems in chemistry.
An open system allows both matter and energy to be exchanged with its surroundings, while a closed system allows only energy exchange, not matter.
What is the difference between an exothermic and endothermic reaction?
In an exothermic reaction, energy is released, leading to a temperature increase in the surroundings. In an endothermic reaction, energy is absorbed, resulting in a temperature decrease in the surroundings.
What is the heat of reaction?
The heat of reaction, represented as ΔH, is the change in enthalpy between the products and reactants of a chemical reaction, indicating whether the reaction is exothermic or endothermic.
How is the rate of a chemical reaction defined?
The rate of a chemical reaction is the change in concentration of reactants or products per unit time.
What are some methods for measuring reaction rates?
Reaction rates can be measured by monitoring changes in volume of gas evolved, mass of solid formed, decrease in mass due to gas evolution, intensity of color of solution, formation of a precipitate, pH changes, or temperature changes.
What factors can change the rate of a chemical reaction?
Surface area of solid reactants, concentration of reactants, gas pressure, temperature, and the presence of catalysts can all influence reaction rates.
Explain how surface area affects reaction rate using collision theory.
Increasing surface area exposes more reactant particles, leading to more collisions and therefore a higher reaction rate, without changing the energy of colliding particles or the activation energy.
How does concentration affect reaction rate according to collision theory?
Higher concentration means more particles per unit volume, increasing the frequency of collisions and thus the reaction rate, without altering the energy of colliding particles or activation energy.
