Topic 6 - Rate of Reaction Flashcards
(32 cards)
how does the rate change over time
1) start(steep line)
2) middle(curving line)
3) end (flat line on graph)
1) rate is fastest at very start because concentration of reactants is highest
2) rate slows down because concentration of reactants decreases as they get used up
3) rate is 0 because all reactants are used up so reaction has stopped
what is reversible reaction
when products can react to form original reactants
what is the symbol for a reversible reaction
what happens as reactants react in a reversible reaction
as they react, their concentration falls- so forward reaction slows down BUT as more products are formed their concentration rises so backwards reaction speeds up
what happens when a reversible reaction is at equilibrium
soon forward and backwards reaction will go at the same rate
is a reversible reaction endo or exothermic
if the reaction is endothermic one way, it will be exothermic the other way
what happens to the energy in a reversible reaction
the energy transferred from surroundings by endothermic is equal to energy transferred to surroundings by exothermic
what explains the rate of reaction
the Collison theory- in terms of particles of reactants colliding with each other
what does the rate of reaction depend on
- the collision frequency
- the energy transferred during a collision as particles have to collide with enough energy for it to be succesful
what is activation energy
the minimum amount of energy needed to start a reaction
what is the link between rate of reaction and collisions
more collisions increases rate
what do catalysts do
increases rate of reaction (speed it up)
how do catalysts work
increases rate by providing a different pathway for the reaction that has a lower activation energy
- not used up in reaction
what do enzymes work as
biological catalysts
what does using a catalyst look like on a reaction profile
- a lower curved line to show the less activation energy
how does pressure affect rate
increases pressure of gas, increases the number of particles in a certain volume. this means particles collide, more often increasing rate
how does concentration affect rate
if a solution is made more concentrated, there are more particles in the same volume
this makes collisions more frequent
how does surface area affect rate
breaking up a solid into smaller pieces increase SA: V
for the same volume of solid, the particles will have more area to hit - so collisions will be more frequent
- the larger the SA the faster the rate
how does temperature affect rate
the higher the temperature the faster the rate
- particles have more energy and move faster so collisions are more frequent
also more particles have the activation energy so more collisions are successful
how do you calculate the mean ate of reaction from a graph (2)
- change in y/ change in x
2.draw a tangent at the point and find its gradient
what is the rate of a reaction
how fast the reactant are changed into products
what is an example of a slow reaction
rusting iron
what is an example of a moderate reaction
magnesium reacting with acid
what id an example of a fast reaction
explosions
