Physical Unit 1.5: Kinetics Flashcards
reactions can only take place when…
particles collide with energy greater than or = to the activation energy
define activation energy
minimum energy needed for particles to successfully react
why do most collisions not lead to a reaction?
particles have energy less than the activation energy
incorrect orientation
what do different parts of a maxwell-boltzmann distribution curve represent?
shows probability of energy of particles in a gas
see notes booklet
what is the effect of changing temperature on the maxwell-boltzmann distribution curve?
same area under curve bc same total # of particles
lower peak
peak shifted right = higher Emp & higher Emean
lots more particles have E > of = EA
only crosses original curve once
what is the effect of changing concentration/pressure on the maxwell-boltzmann distribution curve?
think of both as changing the # of particles in a given volume
lower conc:
lower peak
total # particles decreases so area under curve decreases
Emp & Emean stay the same
fewer particles with E > or = EA
doesn’t cross original curve
what is the effect of a catalyst on the maxwell-boltzmann distribution curve?
lower EA
more particles have E > or = EA
define rate of reaction
speed at which the products are formed from the reactants in a chemical reaction
how does increasing temperature affect the rate of reaction?
increases rate of reaction
bc particles have more KE
more particles have E > or = to EA
so more successful collisions per second
why is the rate of a reaction fastest at the start, slows down over time then stops?
rate is highest at start bc there is the greatest conc. of reagent particles so highest # successful collisions per second
rate slows down bc as time increases, # & conc of reagent particles decreases so there is a decrease in # of successful collisions per second
reaction stops bc limiting reagent is completely used up so no successful collisions per second
how does increasing conc./pressure affect the rate of reaction?
increases rate of reaction
bc increased # of particles in a given volume
so more successful collisions per second
how does adding a catalyst affect the rate of reaction?
increases rate of reaction
provides an alternative reaction pathway of lower activation energy
so more particles have E > or = to EA
so more successful collisions per second
not used up/chemically unchanged
