Rate of Reaction Flashcards
how can you define the rate of reaction
the speed of the reaction
what are the 5 ways to speed up a reaction
increase temperature
increase the concentration of a liquid
increase the pressure of gases
increase surface area of solid
use a catalyst
what is the colllision theory
if a reaction happens:
-particles are constantly moving
-for the collision to be successful the particles must have the right amount of activation energy. the minimum amount of activation energy required for an effective collision is called activation energy
-more frequent collisions
-then new substances are formed
rate of reaction equation
amount of reactant used or amount of product made
/
time taken
what are the units for rate of reaction
the units of the amount of reactant or product divided by the unit of time taken
why does increasing temperature increase the rate of reaction
the particles have more kinetic energy and move faster
so there are more frequent collisions
and more particles have the activation energy
why does increasing concentration increase the rate of reaction
there are more particles
so there are more frequent collisions
why does increasing pressure increase the rate of reaction
there are more particles
so there are more frequent collisions
how do you calculate the surface area of a cube
(length x height) x no of faces
how does increasing surface area increase the rate of reaction
to increase the surface area you need to make the substance smaller eg powdered
this causes more frequent collisions
specific points on catalysts (4)
catalysts speed up a reaction but are not used up
only small amounts are needed
catalysts are specific to a reaction
they are not included in the chemical equation
how do catalysts increase the rate of a reaction
they provide a different pathway for the reaction that has a lower activation energy
how to work out the rate of a straight line (4 steps)
1 - make a triangle using your line
2- work out change in y axi
3- work out change in x axis
4- work out the gradient
how do you work out the rate of a curved line (5 steps)
question will include a value to find
1 - find that point on the curve
2- draw a straight line that touches the point and make a triangle
3- work out the change in the y axis
4- work out the change in the x axis
5- work out the gradient
points to learn about reversible reactions (3)
- the reaction goes both forwards and backwards
- the reactants change into products
- as soon as some products are made, they react to form the reactants
how can you tell if a reaction is exothermic?
the energy change is negative
when is an equilibrium reached
when the rate of forward reaction is the same as the rate of backwards reaction in a closed system
what is a closed system
a system that stops any reactants or products escaping
which three conditions can we change to change the equilibrium
concentration
pressure
temperature
what is the rule for increasing the concentration of a product
if you increase the concentration of a product, it moves to the reactants
what is the rule for increasing the concentration of a reactant
if you increase the concentration of the reactant it moves to the side of the products
steps for presenting an answer about what happens if you increase the concentration of a substance (4 steps)
1 - write the rule
2- write which direction the equilibrium will move
3- write what happens to the amount of product you make
4- write what you make
what is the rule for increasing pressure
if we increase the pressure, the equilibrium moves to the side with less molecules
what is the rule for decreasing pressure
if you decrease the pressure , the equilibrium moves to the side with more molecules
