3.1 Physical Chemistry: .5 Kinetics Flashcards Preview

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Flashcards in 3.1 Physical Chemistry: .5 Kinetics Deck (20)
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the collision theory suggests that a reaction will only take place if three conditions are met.

what are these conditions?

1.) the reactants collide

2.) The collisions occurs with a certain minimum energy, know as the activation energy

3.) the collision has the correct collision geometry


what is meant by rate?

what are the units?

rate is a measur of how much the concentration of substrate changes per unit time

moldm-3 s-1


what is the eqaution for working out rate?

rate= amount of reactant used or product formed/ time taken


what is meant by the activation energy?

the minimum energy needed to start a reaction


why is it that most collisions do not lead to a reaction?



what does the Maxwell-Boltzmann distribution show you?

it tells us about the distribution of energy amongst the particles


explain how increasing the concentration of the reactants in a reaction affects the rate of reaction  

-increasing the concentration of products increases the collision frequency

-leading to a faster rate of reaction

-i.e more successful collisions per second, per cm3


how does doubling the concentration affect the rate of reaction? represent this in a equation

-doubling the concentration doubles the number of particles per cm3

-therefore doubling the number of successful collisions per second,

-so the collision frequency is doubled meaning the rate of reaction is 2 times faster

[C2 = 2 x C1]


show an increase an concentration (x2) on a molecular distribution graph

and a formula to represent this



how can an increase in pressure be achieved

-increasing the pressure of a gas can be achieved by reducing its volume whlist leaving all particles the same


explain how increasing the pressure would affect the rate of reaction

-increasing pressure has the same effect as increased concentration

-so it leads to an increased collision frequency which leads to a faster rate of reaction

-i.e more successful collisions per second, per cm3


on molecular energy distribution graph why does the curve start at (0,0)

because no molecules have 0 energy


what is the EMP on a molecular energy distribution graph

most probably energy


what is the E mean on a molecular energy distribution graph?

the average energy


what does the area under a molecular energy distribution graph equal to?

the total number of molecules


explain how does an increase in surface area affects the rate of reaction?

-when a solid reacts, only the particles on the surface are available for reaction

-if the particles i broken up into smaller pieces it's surface area gets bigger and more particles (surfaces) are available for collisions

-therefore the collision frequency increases as there are more successful collisions per second

-increasing the rate of reaction 


explain how what would happen to the rate of reaction if there was a rise in temperature

represent this in a graph

- a rise temperature will result in an increased rate of reaction

-this is because at a higher temperature there are more particles with energy greater than or eqaul to the activation energy

-therefore more successful collisions per second


what is a catalyst?

a substance that speeds up the rate of reaction and is left chemically unchanged, so it can be reused


how does a catalyst speed up a reaction?

a catalyst provides an alternative pathway for the reaction which has a lower activation energy