Chapter 10 Key Concepts Flashcards
4 factors that change the rate of reaction
Concentration
Temperature
Use of a catalyst
SA of solid reactants
Explain collision theory
Two reacting particles must collide for a reaction to occur
- usually only small no. Collisions lead to chemical reaction
- mostly just collide then bounce off and remain chemically unchanged
3 conditions needed for a reaction to take place
Collide with correct energy. Enough to overcome the Ea barrier of the reaction
Right orientation
Right particle
How does increasing concentration affect ROR
Increase con increases no. Of particles in the same volume.
- closer together hence collide more frequently
- in a given time more successful collisions and increase rate of reaction
How does increasing pressure affect ROR
When gas pressed into smaller volume ,pressure of gas increased.
- con increases as same no. Molecules occupies a smaller volume
- closer together
- collide more frequently
- more effective collisions in the given time
Two ways of measuring the progress of a chemical reaction
- monitoring the removal of reactant
- monitoring the formation of a product
- methods of monitoring
- gas volume
- mass
- colour
- method depends on
- properties and physical states of reactants and products
How to determine rate of reaction if the reaction makes a gas
- monitor vol of gas made at regular time intervals using gas collection
- monitor loss of mass of reactants using a balance
*vol made and mass loss are proportional to change in Con. giving a measure of ROR
Monitoring the loss of mass of reactants using a balance
Eg neutralisation of a carbonate
- add carbonate and acid into conical flask on a balance
- record initial mass
- take more recording at regular time intervals
- reaction complete when no more mass lost and plot mass against time graph.
Industrial processes involving heterogeneous catalysts
Making ammonia in the hater process -Iron Reforming -Pt or Rh Hydrogenation of alkenes -Ni Making sulfur trioxide for sulphuric acid in the contact process -V2O5
Why are catalysts important for sustainability and the economy
lower Ea
- decreasing temperature needed for the process and the energy requirements
- less energy means less electricity or fossil fuels used
Speeding up the rate of reaction
- making the product faster and using less energy cuts cost
- using less fossil fuels cuts CO2 (linked to global warming) emissions
- increasing profitability
What does the Boltzmann Distribution show us
The spread of molecular energies in gases.
Features of a Boltzmann Distribution Curve
Curve starts at origin - No molecules have zero energy.
Curve never meets the x axis at high energy - there’s no maximum energy for a molecule
Area under the curve is the total number of molecules
What’s the effect of higher temperatures on the Boltzmann Distribution curve?
- greater proportion of molecules have energy greater than or equal to the Ea
- greater proportion of collisions will lead to a reaction increasing ROR
- more frequent collisions because molecules moving faster.
*increased energy is more important than increased frequency
What’s the affect of catalyst on the Boltzmann Distribution
Compared to Ea, greater proportion of molecules have energy equal to or greater than the lower activation energy Ec.
- more molecules react to form products
- increased rate of reaction
What isa closed system and why is it important
It’s isolated from its surroundings so the temperature,pressure, and concentrations of reactants and products are unaffected by outside influences
