the rate and extent of chemical change Flashcards
Iron can react with oxygen to form iron oxide. This is also known as rusting.
Is this a fast or slow chemical reaction?
slow
When you strike a match it causes a tiny amount of red phosphorus to be converted to white phosphorus, which then ignites spontaneously in air.
Is this a fast or slow chemical reaction?
fast
what is an example of an extremely fast reaction
explosions like fireworks
how can you measure the rate of reaction
you can measure how fast the products are being used up
or
you can measure how fast the products are being used
what is the rate of a chemical reaction
how fast the reactants are changed into products
what does a steeper line on a rate of reaction graph mean
that the rate of reaction is faster
what does a less steep line on a rate of reaction graph mean
the rate of reaction is slower as the reactants are used up
particles must collide with enough _______ in order to _______
energy
react
what is collision frequency
how often the particles collide.
the more collisions there are the faster the reaction is
what is the minimum amount of energy that particles need to react called
activation energy
why do particles need to meet their activation energy in reactions
activation energy is the minimum amount of energy that particles need to break the bonds in the reactants and start the reaction
what happens when there are more particle collisions
the rate of reaction will increase
what is the formula for the rate of reaction
rate of reaction = the amount of reactant used or the amount of product formed/ time (s)
what are different factors that affect the rate of reaction
- temperature
- surface area
- concentration of a solution or the pressure of gas
- the presence of a catalyst
how can we increase the rate of reaction
by increasing the number of successful collisions between the reacting particles
how does increasing the temperature increase the rate of reaction
- the temperature is increased making the particles move faster
- as they move faster they are going to collide with each other more frequently
- the faster they move the more energy they will have so more of the collisions with have the energy to make the reaction happen
how does increasing the concentration or pressure increase the rate of reaction
- if the concentration or pressure is increased it means there will be more particles per unit of volume
- if there are more particles it means there will be more collisions which increases the rate of reaction
how does increasing the surface area increases the rate of reaction
by increasing the surface area it increases its surface to volume ratio.
which means that for the same volume for solid the particles around it will have more area to work on so the collisions will be more frequent
what is a catalyst
a substance that speeds up a reaction without being chemically changed or used up in the process
how do catalysts increase the rate of reaction
they decrease the activation energy by providing an alternative reaction pathway with a lower activation energy
why type of catalyst are enzymes
biological catalysts meaning they catalyse in living things
When considering how a condition will affect the rate of reaction, you have to consider how it will affect the………
frequency of collisions
and the energy of the particles
Explain how the rate of reaction changes with increasing temperature.
Particles will have more energy
Particles will collide more frequently
More successful collisions
Higher rate of reaction
Which form of magnesium would give the highest rate of reaction?
powder form as there is a high surface area so it will react more quickly
what are some examples of catalysts
- cobalt
- enzymes
- nickel
Should you include the catalyst in the chemical reaction as one of the reactants?
no
why isnt a catalyst included in a chemical reaction as one of the reactants?
because it is not chemically changed or used up in the reaction so its being used up in the reaction itself so its not included
Do transition metals make good catalysts?
yes
what does this sign mean in terms of a reaction ➔
that it is a one way reaction
what does this sign mean in terms of a reaction ⇌
that the reaction is reversible
what happens in reversible reactions
as the reactants react their concentrations will fall so the forward reaction will slow down. but as more and more products are being made up the concentration will rise and the backward reaction will speed up
what is equilibrium
after a while in reversible reactants the forwards reaction will be going at the exactly same rate as the backward reaction
what is happening at equilibrium
both reactions are still happening but there is no overall effect which means the concentrations of the reactants and products wont change
what is a closed system
that none of the reactants or products can escape and nothing else can get in
where does equilibrium have to take place for it to be reached
in a closed system
when a reaction is at equilibrium doe sit mean that the amount of reactants and products are equal
no it means the concentrations of the reactants and the products remain constant
if the equilibrium lies to the right what does it mean
the concentration of products is greater than the concentration of reactants
if the equilibrium lies to the left what does it mean
the concentration of reactants is greater than the concentration of products
what are the conditions that affect the position of the equilibrium
- the temperature
- the pressure ( only affect equilibrium involving gases)
- the concentration of reactants and products
in reversible reactions if the reaction is _________ in one direction it will be ___________ in the other
endothermic
exothermic
What happens in an endothermic reaction?
heat is taken in from the surroundings
what does collision theory state
theory states that for particles to react, they have to collide with sufficient energy
what does La ch ateliers principle state
if you try to change the conditions of a reversible reaction, the position of the equilibrium will shift to try and counteract the change
At equilibrium, if there are more products than reactants, we say that the position of equilibrium lies:
to the right
what can la chateliers principle useful for
it can be used to predict the effect of any changes you make to a reaction system
in reversible reaction if one direction is exothermic then the other one is
endo thermic
2NO2(g) ⇋ N2O4(g) (-24 kJ mol-1)
In the reaction above, the (-24 kJ mol-1) tells us that the forward reaction is:
exothermic because it is negitive
An increase in pressure moves the position of equilibrium to whichever side has the:
least number of molecules
In a reversible reaction, changes in pressure will only affect substances that are in the:
gaseous state
What are the three factors that affect the position of equilibrium?
temperature
pressure
concentration
N2(g) + 3H2(g) ⇋ 2NH3(g)
In the above reaction, increasing the pressure will:
shift the position of the equilibrium to the right
if you decrease the temperature in a reversible reaction the equilibrium will move….
in the exothermic direction to produce more heat. which means you will get more products for the exothermic reaction and less products for the endothermic reaction
if you increase the temperature in a reversible reaction the equilibrium will move..
in the endothermic reaction to try and decrease the temperature. which means you ill get more endothermic products and less exothermic products
what happens if there is a decrease in pressure in a reversible reaction
the equilibrium will try to increase it and move in the direction with the most molecules of gas
what happens if you change the concentration of either of the reactants or products in a reversible reaction
the system will no longer be at equilibrium
how does the reaction system respond when you change the concentration in a reversible reaction
when you change the concentration the system will no longer be at equilibrium so they system responds by bringing itself back to equilibrium
how does changing the concentration in a reversible reaction affect the amounts of products and reactants produced
if you increase the concentration of reactants the system tries to decrease it by making more products
if you decrease the concentration of reactants the system tries to increase it by making more products
