Chapter 10 - Reaction Rates and Equilibrium Flashcards
How does increasing temperature affect the rate of reaction?
The rate of reaction is greater because particles have more kinetic energy, so there is a greater proportion of molecules with energy greater than or equal to the activation energy. Therefore there are more frequent successful collisions between particles.
How does increasing concentration/pressure affect the rate of reaction?
The rate of reaction is greater because there is a greater number of molecules per unit volume, so there are more frequent successful collisions between particles.
How does increasing surface area of a solid affect the rate of reaction?
The rate of reaction is greater because a greater proportion of molecules are exposed to react, so there are more frequent successful collisions.
What effect does a catalyst have on the rate of reaction?
The rate of reaction will increase because a catalyst provides an alternate reaction pathway with lower activation energy, so a greater proportion of molecules will have energy greater than or equal to the activation energy and will be able to react.
What is meant by rate of reaction?
The change in concentration of reactant or product in a given time.
What makes a successful collision?
Particles need to collide in the correct orientation and with sufficient energy.
How can progress of a reaction be followed?
By monitoring the formation of product or the removal of reactant.
What are two ways of determining rate of reaction when a gas is produced?
By measuring the mass of reactants lost or the volume of gas produced.
What are the main properties of a catalyst?
They are not used up in the reaction.
They may form an intermediate by reacting with the reactant, or provide a surface for the reaction.
They are regenerated at the end of the reaction.
What is a homogeneous catalyst?
A catalyst that is the same state as the reactants.
What is a heterogenous catalyst?
A catalyst that is a different state to the reactants.
How does a homogeneous catalyst work?
It reacts with the reactants to form an intermediate. The intermediate breaks down to give the product and the catalyst is regenerated.
How does a heterogeneous catalyst work?
The reactants are adsorbed onto the surface of the catalyst where they react, and then the products leave the surface of the catalyst by desorption.
What are the benefits of using a catalyst?
It lowers the activation energy, so it is cheaper as reactions require less energy, so there is more profit and products are made faster.
They lower carbon dioxide emissions as less fossil fuels are used.
What are the main features of the Boltzmann distribution?
No molecules have zero energy.
The area under the curve is equal to the number of molecules.
There is no maximum energy.
How does the Boltzmann distribution curve change when temperature is increased?
The curve is shifted to the right as more molecules have higher energy. A greater proportion of molecules have energy higher than the activation energy.
What is a dynamic equilibrium?
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.
What is Le Chatelier’s principle?
When a system in dynamic equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of that change.
What is the effect of a catalyst on equilibrium?
Does not change the position as it speeds up the rate of both forward and reverse reactions equally.
What is the effect of increasing pressure on equilibrium?
The equilibrium will shift to the side with less gas molecules.
What is the effect of increasing temperature on equilibrium?
The equilibrium will shift in the endothermic direction.
What is the effect of increasing concentration on equilibrium?
The equilibrium will shift in the opposite direction of the substance being added.
