Chapter 10 - Reaction rates and Equiillibrium Flashcards
(26 cards)
What is rate of reaction?
How fast a reactant is being used up or how fast a product is being formed
How can rate of reaction be changed?
Concentration
Temperature
Catalysts
Surface area of solid reactants
Pressure of gases
What is collision theory?
Two reacting particles must collide effectively for a reaction to occur
What conditions are required for particles to collide successfully?
Particles collide with correct orientation
Particles have sufficient energy to overcome activation energy
How does increasing the concentration of a reactant affect the rate of reaction?
Rate of the forward reaction increases
So more product is produced
Increased concentration means more particles in the same volume
So particles collide more frequently so there will be more effective collisions
How does increasing the pressure of gas affect the rate of reaction?
Concentration of gas moles increases as the same number of gas moles occupies a smaller volume
Gas molecules are closer together so will collide more frequently and have more successful collisions
How can the progress of a reaction be followed?
Monitoring the removal of reactant (decreasing concentration)
Monitoring the formation of a product (increasing concentration)
How can progress of reaction be followed with reactions that produce gas?
Monitoring volume of gas produced at regular time intervals
Monitoring loss of mass with an electronic balance
How can rate of reaction be calculated from a graph measuring mass loss?
Plot mass lost against time
Draw tangent on the curve at the time you want to know the rate of reaction
Rate of reaction is the gradient
What does a catalyst do?
Speeds up the rate of reaction without undergoing a permanent change
Not used up in reaction
Will react with a reactant to form an intermediate
Catalyst is regenerated
Provides and alternate reaction pathway that lowers activation energy
What is an intermediate?
A species formed during a reaction that reacts further and is not present in the final products
What is a homogeneous catalyst?
Same physical state as the reactants
What is a heterogeneous catalyst?
Different physical state from the reactants
Usually a solid catalysing a gas reaction
Why are catalysts important?
Increase the rate of industrial reactions so more product is made in the same amount of time
Lowers the activation energy so less energy is required on high temperatures of pressure
Increases profits
Reduced energy means less fossil fuels are used to produce energy
What are the features of the Boltzmann distribution?
No molecules at zero energy
Area under the curve is equal to the total number of molecules in the system
No maximum energy for a molecule - the curve never touches the x-axis
Activation energy marked on
How does temperature affect the Boltzmann distribution?
At high temperatures
More molecules with energy equal to or higher than the activation energy
Lower peak and more to the right
More frequent collisions as increased kinetic energy so higher probability of successful collisions
How do catalysts affect the Boltzmann distribution?
Curve shape stays the same
With a catalyst the activation energy is lower (more to the left)
What is a reversible reaction?
A reaction where the forwards and reverse reaction both happen simultaneously
What is dynamic equilibrium?
Rate of the forwards reaction is equal to the rate of the reverse reaction
Concentrations of the products and reactants to not change
Closed system
What is a closed system?
A system that is isolated from the surroundings
Temperature, pressure and concentrations are unaffected by outside influences
What is le Chatelier’s principle?
When a system in equilibrium is subjected to an external change the system readjusts itself to minimise the effect of that change
How do changes in concentrations affect equilibrium?
More products added means equilibrium shifts to the left
More reactants added means equilibrium shifts to the right
How do temperature changes affect equilibrium?
Increased temperature shifts equilibrium to the endothermic side
Decreased temperature shifts equilibrium to exothermic side
How do pressure changes affect equilibrium?
Increased pressure shifts to the side with less gas moles
Decreased pressure shifts to the side with more gas moles
