10- Reaction Rates And Equilibrium Flashcards
Rate of a chemical reaction definition
Measures how fast the reactants are being used up or products are being formed
Rate of reaction (concentration) definition
The change in concentration of a reactant or product in a given time
What conditions are required for a reaction to take place
The particles collide with the correct orientation
The particles must have sufficient energy to overcome the activation energy barrier of the reaction
Activation energy definition
The minimum amount of kinetic energy required for a reaction to occur
What 5 things can alter the rate of a chemical equation
Increasing temperature
Increasing SA
Increasing pressure
Increasing concentration
Use of a catalyst
How does temperature affect the rate of reaction
Temperature increases the rate of reaction by…
Increases KE of particles
Greater proportion of the particles will have at least the activation energy - more effective collisions
Causes them to move faster and collide more frequently increasing the chances of effective collisions
How does concentration / pressure alter rate of a chemical reaction
Increasing concentration/pressure increases the rate of reaction
It increases the number of particles in the same volume
Particles are closer together
Collide more frequently
More likely to be more effective collisions
How do catalysts affect rate of reaction
Catalysts increase rate of reaction
They lower the activation energy
By providing an alternative reaction pathway
A greater proportion of particles will have enough energy to react
What are the different types of ways to measure reaction rates
How quickly the reactants are used up = removal of reactant
How quickly the products are formed = formation of a product
List of ways of measure rate of reaction practicals
Record then graph …
- colour changes in solutions
- mass change
- volume of gas produced
- pressure changes in gasses
- changes in conductivity
Monitoring the loss of mass of reactants using a balance practical
1) add reactants to conical flask
2) record initial mass
3) add catalyst
4) record mass at regular intervals until no change
Monitoring volume of gas produced at regular time intervals using gas collection
1) add reactants to conical flask and replace bung
2) record the initial volume
3) add catalyst
4) measure volume at regular interval changes
Catalyst definition
A catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged by the end of the reaction
Heterogeneous catalyst definition
A reaction in which the catalyst has a different physical state from the reactants
Reactants = gases Catalyst = solid
How does a heterogenous catalyst operate
Reaction takes place on surface of the catalyst
Reactant is absorbed onto surface (forms weak bonds)
Product leaves through desorption
Homogenous catalyst definition
A reaction in which the catalyst and the reactants are in the same physical state
Aqueous
How do homogeneous catalysts operate
Catalysts react with the reactants to form an intermediate species
Which breaks down to give products and regenerates the catalyst
What is the economic importance of catalysts
- Catalysts lower the production costs
By producing more products in shorter time
And reducing the energy required by using lower temperatures - change the properties of a product to make it more useful
Why are catalysts good for environmental sustainability
-Preserves energy
-Reduces waste
By producing fewer pollutants as higher at economy
Convert harmful pollutants into safer ones
What is Boltzmann distribution
The spread of molecular energies in gases
What does Boltzmann distribution curve show
Shows the different kinetic energies a number of molecules have in a substance
How does increasing temperature affect a Boltzmann distribution curve
Temperature increases the average energy of the molecules - molecules have higher energy
The graph will stretch
- the peak will be lower
- and further along the x axis
- area is the same
How do catalysts affect the Boltzmann distribution curve
Activation energy is lower on graph
More particles in effective collisions area
Dynamic equilibrium definition
The equilibrium that exists in a closed system when the rate of the froward reaction is equal to the rate of the reverse reaction and concentration do not change
