5 Kinetics Flashcards
explain kinetic theory
for a chemical reaction to take place particles need to collide.They need to collide with correct orientation and they need to collide with energy the same or more than the activation energy
define activation energy
the minimum energy particles must have upon collision for a successful reaction to take place
explain how increasing the temprature increases the rate of reaction
high temperature means particles have more energy increasing the speed of particles and so increasing the frequency of successful collisions
explain how increasing the conecntraion of solution increases the rate of reaction
there are more particles in a given volume increasing the frequency of successful collisions
explain how pressure increases the rate of a gas reaction
there are more particles in a given volume increasing the frequency of successful collisions
explain how surface area of solid reactants increase the rate of reaciton
by breaking solid lumps into smaller particles means more particles are available to collide with molecules in a gas or a liquid increasing the frequency of successful collisions
what is the meaning of the term catalyst and how does it work
A catalyst is a substance that increases the rate of a chemical reaction without being changed.It provides an alternative reaction pathway with a lower activation energy
what happens in endothermic reaqctions with refrecne to the sourrouindings and what is the sign of ∆H
surroundings gets cooler as heat energy is given in
what happens in exothermic reaqctions with refrecne to the sourrouindings ∆H
surroundings gets hotter as heat energy is given out
is ∆H negative of positiove for endothermic reactions state why
positive because the products have more energy than the reactants
is ∆H negative or positive for exothermic reactions state why
negative because the products have less energy than the reactants
deifne rate of reaction
the change in the concentration of product or reactant over time
what is the equation used to calculate rate of a reaction
amount of reactant used or product formed/time
explain why most collisions do not lead to a reaction.
because most particles collide with energy less than activation energy.Particles need to collide with energy greater or equal to activation energy to react and stick to form a product
what is a trasnition state
the species that exists at the top of the curve of an enthalpy diagram
what does the Maxwell-Boltzmann distribution tell us about the distribution of energy amongst the particles
no particles have zero energy
most particles have intermediate energies - around the peak
few particles have very high energies -RHS of the curve
where is the most probable energy on the M.B.D curve
at the peak
where is the average energy on the M.B.D curve
to the left of the peak(most probable energy)
what does the x axis on the M.B.D curve represent
energy
what does the y axis on the M.B.D curve represent
number of particles
what does the area under the M.B.D curve represent
the number of particles
explain what happens to the sshape of the curve when temperature increases
the peak of the curve is lower and shifts to the right and the endof the curve is raised higher so more pearticles have energy greater than Ea
what is the abbreviation used for activation energy
Ea
why is the total area under the graph the same for different temperatures
because are under the graph only represents the total number of particles
with reference to the M.B.D explain why an increase in temperature decreases the rate of reaction
more of the particles have energy greater than or equal to Ea so more particles have sufficient energy to react increasing the frequency of successful collisions
state why the M.B.D curve starts at the origine
because there are no particles with zero energy
with reference to the M.B.D explain why a decrease in temperature decreases the rate of reaction
because fewer particles will have energy more than or equal to activation so less particles have suffieicnet energy to react decreasing the frequency of successful collisons
explain why a small increase in temperature has large effect on the initial rate of reaction
a small increase in temperature results in significantly more particles colliding with energy equal to or greater than activation energy
with reference to the M.B.D explain how a catalyst increases the rate of a reaction
a catalyst provides an alternative reaction pathway with a lower activation energy and so more particles will have energy equal to or greater than activation energy and more particles will have sufficeint energy to react increasing the frequency of successful collisions and therefore increases the rate of reaction
how would the M.B.D curve look when a catalyst is added and state the how it affects the activation energy
Ea on the axis will shift to the left and so more particles will have energy greater or the same as Ea
describe how a catalyst affects enthalpy change
they have no effect on the enthalpy change
describe how a catalyst affects activation energy
it provides an alternative reaction pathway with a lower the activation energy so more particles will have energy greater or equal to Ea
describe how a catalytic coverter looks like
converter is a honeycomb coated with platinum and rhodium metals.These are the catalysts.Has large Surface ara
explain how a catalytic convertor work with reference to adsorption and desorption
adsorption: gases form weak bonds with metal atom of surface of the catalyst.The bonds must be strong enough to hold the gases for long enough to react and weak enough to relase the products easily
desporption: products break away from metal atom freeing up more room on the surface of the catalyst for more gases to react
what does the area under a particular region of a curve represent
number of particles that can react
