1.5- kinetics Flashcards
collision theory
for particles to react they must:
-collide in the right direction
-collide with the activation energy
why are most collisions unsuccessful
they dont have the minimum Ea needed to break bonds and allow the particles to react
how to increase rate of reaction (2)
-more frequent collisions (increase particle speed/have more particles)
-more successful collisions (particles have more energy/lower activation energy)
maxwell-boltzmann distribution
what does it show
molecules in gases have different energies
maxwell-boltzmann distribution
why does the curve start at 0,0
no molecules have no energy
maxwell-boltzmann distribution
what does the peak of the curve show
most probable energy of a single molecule
maxwell-boltzmann distribution
what does the part after the peak of the curve show
mean energy of all molecules
maxwell-boltzmann distribution
why does the curve not touch the x-axis
some molecules have very high energy
how does increasing concentration increase reaction rate (4)
-more particles in the same volume
-particles packed closer together
-more frequent collisions
-more successful collisions per second
what does the line in a graph of rate against concentration show
the graph shows a straight line through the origin, showing that rate and concentration are directly proportional
how does increasing surface area increase reaction rate (2)
-surface is exposed to other reactant particles
-more frequent collisions, so more successful collisions
how does a small increase in temperature increase reaction rate (3)
-small increases in temp lead to a big increase in reaction rate
-for every 10 degrees rise in temp, the rate doubles
-there is a significant increase in the number of molecules with Ea
how does increasing temperature increase reaction rate (3)
-particles have more kinetic energy
-more particles have at least the minimum Ea
-more frequent collisions, so more successful collisions
maxwell-boltzmann distribution
what happens to the curve at a higher temperature
distribution changes so the peak is lower and the curve shifts to the right
maxwell-boltzmann distribution
what happens to the curve at a lower temperature
distribution changes so the peak is higher and the curve shifts to the left
when must a catalyst be regenerated/renewed
when there are impurities in reactants
what is a catalyst + how does it increase reaction rate (3)
-substance that increases reaction rate without being used up
-provides an alternate reaction pathway with a lower activation energy
-more particles have energies greater than Ea, so there are more frequent, successful collisions
what is a homogeneous catalyst
-catalyst is in the same physical state as reactants
what is a heterogeneous catalyst (2)
-catalyst is in a different physical state from reactants
-they work by absorbing reactant molecules
why does using a catalyst make economic sense (3)
-used without being used up
-allows more product to be made per unit time
-temp is lower, so running costs are cheaper
equation for rate
rate= change in measured factor/change in time
