REACTION RATES AND EQUILIBRIUM Flashcards
What is the rate of reaction
the change in concentration/amount of a reactant or product per unit time
2 key points of collision theory
For a reaction to occur particles must collide in the right direction
they must also have a minimum amount of kinetic energy
What is activation energy
the minimum amount of energy required for a reaction to occur
How does temp affect rate of reaction and how Boltzmann curve is affected
temperature increases rate as more particles will collide and will have have more energy than Ea. So curve shifts right, peak is lower, line higher at Ea.
(if lower temp, curve shifts left, peak is higher, line is lower at Ea)
How does concentration and pressure affect rate of reaction
Pressure increases rate as collisions will be more frequent due to particles closer together, so a higher chance of reaction
Concentration increases rate as particles will be closer together and collide more often, so higher chance of reaction
BOTH HAVE SAME EFFECT
what is a catalyst
Catalysts are substances that increase rate of reaction by providing an alternate pathway that has a lower activation energy, catalyst is chemically unchanged at the end of the reaction
What is a heterogeneous catalyst and give an example
a catalyst that is in a different state to the reactants
Haber process - solid iron catalyst whereas
nitrogen hydrogen and ammonia are all gases
What is a homogeneous catalyst and how do they work
and give an example
a catalyst that is in the same state as the reactants (usually aqueous)
form an intermediate with the reactants which reacts again to form products
using sulphuric acid to make an ester
How do catalysts affect rate of a reaction on a Boltzmann distribution
catalyst shifts the Ea. to the left so more particles exceed the Ea. so reaction happens quicker and more readily
How are catalysts used in industry and why is this useful
lower temperature needed for a reaction (safer, cheaper to produce a reaction)
speed up reaction by providing alternate pathway ( better for effectiveness standpoint)
change properties of the product
could lead to less waste being produced, better atom economies
How can rates be measure in experiments
rate of precipitate formation - place a cross on a piece of paper, time taken for cross to disappear
rate of mass lost by gas - place reaction on a scale a measure the mass lost as gas is lost
volume of gas produced - measure how much gas is produced at certain intervals using a gas syringe
How can rate be calculated from a graph
calculate the gradient ( tangent gradient if curved graph ) using change in y / change in x
What is a dynamic equilibrium
Where the rate of the forwards reaction is the same as the rate of the backwards reaction so the concentration of each substance remains constant
ONLY OCCURS IN CLOSED SYSTEMS
what is le chateliers principle
if a reaction at equilibrium is subject to a change in conditions, the position of equilibrium will move to counteract the change
What does increasing concentration of a substance do the equilibrium of a reaction
it will shift to the opposite side of the reaction subject to the concentration increase
(ONLY WORKS IF REACTION IS IN HOMOGENEOUS EQUILIBRIA)
