Chapter 10 - Reaction rates and equilibrium (MODULE 3) Flashcards
What does the rate of a reaction measure
how fast a reactant is being used or how fast a product is being formed
what is the formula for rate of reaction
change in concentration / time
What are the units for rate of reaction
mol dm^-3 s^-1
When is the rate of reaction the fastest
at the start of the reaction
When does rate of reaction = 0
when all the reactants have been used up
What does the collision theory state
two reacting particles must collide for a reaction to occur
What 4 factors affect rate of reaction
concentration / pressure in gases
temperature
use of a catalyst
surface area of solid reactants
what two conditions are required for a collision to be successful
correct orientation, sufficient energy
How does increasing concentration affect rate of reaction
increases - more frequent collisions as particles are closer together, so more frequent successful collisions
How does increasing pressure affect the rate of reaction
particles are closer together so more frequent collisions, more frequent successful collisions
What are two ways of measuring the progress of a reaction for solids
speed of removal, speed of formation of product
What are two ways of measuring the progress of a reaction that involves a gas
monitoring volume of gas produced with a gas syringe, monitoring loss of mass using a balance
What does a catalyst do
provides an alternate reaction path way with a lower activation energy
What is a way that a catalyst can speed up a reaction
form an intermediate product which reacts faster with the reactant, and then is reformed
How does a reaction profile diagram change with the use of a catalyst
the peak is lower
What are the two types of catalysts
homogeneous and heterogeneous
What is a homogeneous catalyst
- what is an example
when the catalyst is the same state as the reactants
- sulfuric acid catalyst for ester production
What is a heterogeneous catalyst
- give an example
when the catalyst is of a different state to the reactants
- iron in the haber process
- nickel in alkene hydrogenation
How do heterogeneous catalysts often work
reactant molecules are adsorbed (weakly bonded) onto the surface of the catalyst, then leaves the surface by desorption
Why are catalysts good for the environment
less energy is required for a reaction to take place, and so less fossil fuels need to be burned making catalysts more sustainable
- also the catalysts are not used up
What does the boltzmann distribution show
the spread of molecular energies in gases
What are on the axis of boltzmann distributions
- what else is depicted
number of molecules on y axis,
energy on x axis
- activation energy on x axis
What are three key features of the boltzmann distribution
- no molecules have 0 energy
- area under curve is equal to total number of molecules
- no maximum energy for a molecule
What is the effect of an increase of temperature on a boltzmann distribution
average energy increases so peak is lower and further to right, area under curve is same
