Rates and Extents of Chemical Reactions Flashcards
(23 cards)
How do you calculate the rate of a reaction?
Rate of reaction = amount of product made or reactant used up ÷ time taken.
What are the three possible units of rate?
g/s or cm³/s or mol/s.
What five factors affect the rate of reaction?
Temperature, concentration, pressure, surface area and use of a catalyst.
How does increasing temperature increase reaction rate?
Particles have more kinetic energy so there are more frequent successful collisions per second, each collision has more energy, so it is more likely to reach activation energy.
How does increasing pressure and concentration increase reaction rate?
The more particles in a given volume, the more successful collisions per second. Rate is proportional to concentration.
How does increasing surface area increase reaction rate?
There are more exposed particles per given mass, meaning there will be more frequent successful collisions.
How does a catalyst increase reaction rate?
It provides a surface for an alternative pathway for the reaction, which reduces the activation energy, meaning there are more frequent successful collisions per second.
What is the collision theory?
For a chemical reaction to take place, particles must collide together with sufficient energy to break the bonds holding the reactants together.
What is activation energy?
The minimum amount of energy particles must have in order to react.
Why do rates of reaction slowly down as they progress?
The concentration of reactants decreases as they are converted into products, leading to fewer collisions and a reduced rate of successful reactions.
How do catalysts increase reaction rate?
They provide a different pathway for the reactions that have a lower activation energy.
What symbol represents a reversible reaction?
Reactants⇌Products.
What is a reversible reaction?
It is a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously.
What is Le Chatelier’s principle?
If a system is at equilibrium and a change is made to any of the conditions, the system responds to counteract this change.
What is equilibrium?
When the forward and reverse reactions occur at the same rate (in a closed system).
What three factors affect the rate of equilibrium?
Concentration, temperature and pressure.
How does concentration affect the rate of equilibrium?
If the concentration of a reactant is increased, more products will be formed until equilibrium is reached again. If the concentration of a product is decreased, more reactants will react until equilibrium is reached again.
How does temperature affect the rate of equilibrium?
If the temperature is increased, the equilibrium will favour the endothermic reaction. If the temperature is decreased, the equilibrium will favour the exothermic reaction.
How does pressure affect the rate of equilibrium?
If the pressure is increased, the equilibrium will favour the side with the fewest moles of gas. If the pressure is decreased, the equilibrium will favour the side with the most moles of gas.
What is a closed system?
Where no reactants or products can escape, only heat can be exchanged freely.
What is the yield of a reaction?
It is the amount of product obtained in a chemical reaction, often expressed as a percentage (can be used to calculate reaction efficiency).
What does dynamic equilibrium mean?
A state in a reversible reaction where the forward and reverse reactions occur at the same rate, resulting in no net change in the concentrations of reactants and products, even though the reactions are still ongoing.
Why are industrial conditions often chosen as a compromise?
To balance factors like product yield, reaction rate, and economic considerations, rather than solely optimising for one factor.
