kinetics Flashcards
wat are the conditions required for a reaction to take place?
the particles collide in the right direction. they need to be facing each other in the right way.
they collide with at east a minimum amount of kinetic energy.
what is the activation energy?
the minimum amount of kinetic energy that two colliding particles need to react. they need this amount of energy to break the bonds to start the reaction.
what does a maxwell-boltzmann Distribution curve show?
it shows how many particles there are and how much kinetic energy they have - they also show the activation energy.
what happens earn you increase the temperature in a reaction?
the reaction occurs faster. the particles will have more kinetic energy and will move faster and so there will be a greater proportion of them that have at least the activation energy and be able to react. this pushes the distribution curve to the right and does.
how does concentration affect the reaction?
increasing the reaction speeds up the reaction. if you increase the conc there will be more particles in a given volume of the solution, particles will therefore collide more frequently. this means that there will be more successful collisions per second and so the reaction will be quicker.
how does the pressure affect the reaction?
increasing the pressure speeds up the reaction. this can only occur i the gases are in a closed system. it means that there are more molecules in a given volume of gas.
what does a catalyst do?
it provides an alternate reaction pathway that has a lower activation energy. this means that more of the particles will have enough energy to react. there will therefore be more collisions per second so the rate will increase, they are chemically unchanged at the end of the reaction.
what doe the rate of reaction tel us?
it is the change in amount of product or reactant per unit time
how do you work out rate of reaction from a graph?
if you are working with a graph that shows the amount of product or reactant produced over time, then the rate is just the gradient .
how do you work out the initial rate of a reaction?
this is the rate at the start off the reaction. to find this in a concentration time graph calculate the gradient of the time tangent at time
how do you calculate rates from experimental data?
if you are waiting for a set amount of product to be used or a set amount of reactants to be used up you can use this equation to work out the rate - amount of reactant used or the amount of product formed/ time taken.
what is a heterogeneous catalysis?
a catalyst that is in a different phase from the reactants (a different physical state)
the reaction happens on the surface of the heterogeneous catalyst. increasing the surface area of the catalyst will therefore increase the number of molecules that react at the same time and therefore will increase the rate.
how does a heterogeneous catalyst work?
reactant molecules arrive at the surface and bond with the solid catalyst. this is called adsorption. the bonds between the reactant molecules are weakened and break up. this forms radicles. these then get together and make new molecules. the new molecules are then detached from the catalyst which is called desorption.
