Chemistry Paper 2 Flashcards
What is the rate of a reaction?
How fast the reactants change into products
What is an example of a slow reaction?
The rusting of iron
Chemical weathering
What is an example of a moderate speed reaction?
Magnesium reacting with acids to create a gentle stream of bubbles
What is an example of a fast reaction?
Explosions (which happen in fractions of seconds
How can you find the rate of reaction?
Recording the amount of product formed and the amount of product used up pver time
Of you were to plot amount of products formed on the y axis and time on the x what would a reaction with a high rate of reaction look like?
Very steep gradient
What does the rate of reaction depend on?
How frequently particles collide (the more collisions there are the faster the reaction)
The amount of energy the particles have (do they have the activation energy needed to start the reaction)
What is collision theory?
What is activation energy?
The minimum amount of energy needed to start an reaction when 2 particles collide
What is activation energy used for?
To break the bonds of the other compound and start the reaction to make new bonds
How can you increase the raye of reaction?
Surface area (amount of collisions that happen)
Temprature (kinetic energy increasing the amount of collisons that happen, also most particles will be above the activation energy)
Increasing concentration of preasure (more collisions)
Using a cataylist
Why does an increase in temprature increase the rate of reaction?
The particles get more kinetic energy and therefore travel faster. This means that collisions happen more frequently
Furthermore the faster they move the more energy they have and the more likely that will have the amount of activation energy needed to start the reaction
Why does increasing the concentration or preasure increase the rate of reaction?
If a solution is more concentrated then there will be more particles in a space. Therefore collisions will happen more frequently (this is the same with preasure)
Why does increasing surface area lead to a higher rate of reaction?
Breaking up an object into pieces will increase it’s surface area to volume ratio. This mean that there is more area to come in contact with the pther particles meaning that collisions will be more frequent
How do you describe collisions in an exam?
The amount of collisions is more frequent
Not more collisions happen ect
What is a cataylist?
A substance that speeds up a chemcial reaction without being used up
(It is not part of the reaction)
What do cataylists do?
Will they work on everything?
Different cataylists are needed for different reactions. They work by decreasing the amount of activation energy needed for the reaction to happen by providing an alternative reaction pathway. Therefore more collisions result in a reaction happening
What is an enzyme?
A biological catalysts which catalyse reactions in living things
Rate of reaction =
Amount of reaction used or Product formed / time
What is Amount of reaction used or Product formed meausred in?
Normally cm^3 in gas
In solids then g
What are the units for rate?
cm^3/s or g/s
Possible measured in moles
mol/s
How may you measure rate of reaction?
Precipitation (clowdiness)
Colour change
Change in mass (usually gas given off)
Change on volume
How may precipitation and colour change help you work out the rate fo reaction?
You can measure how long it takes for the solition to become opaque or change colours (possibel using a black cross or a cross the colour of the new product and measuring how long ot takes for it to become camoflaged
What are the disadvantages of using precipitation and colour change help you work out the rate fo reaction?
The results will be subjective as some people may have better eyesight.
How may change in mass help you work out the rate fo reaction?
The quicker the mass changes then the quicker the rate of reaction (may use a mass balance)
You make take measurments at regualr intivals so that you can plot a rate of reaction graph
What are the disadvantages of using change in mass change help you work out the rate fo reaction?
You release gas into the room
Can’t do this with poisenes gases easily (you may need good ventilation/gas mask
What are the advantages of using change in mass help you work out the rate of reaction?
It is the most reliable method
How may you measure the amount of gas given off?
Using a gas syringe (the plunger will get pushed back)
How does rhe volume of gas given off let us measure rate of reaction?
The more gas that is given off in the same amount of time the higher the rate fo reaction
Of the same amount of gas given off but quicker
Hwo do you calcuate the rate of reaction on a graph with a curve?
Draw a tangent
What is a reversable reaction?
A reaction that can react back into the products that made it
What happens during a reversable reaction?
As rhe initial products react their concentration falls and that reaction will slow down but the concentration of product/s will increase therefore the opposite (reverse) reaction will start ot happen
…
What is equilibrium in terms of a reaction?
When both reactions are still happening but there is no overal effect (it will also look like nothing is happening
What is a dynamic equilibrium?
When the concentrations of reactants and products have reaced a balnce and won’t change
Will equilibrium be reached in every reverce reaction?
No. Only the ones in a closed system
What does ir mean if the equilibrium lies on the right?
It means that the concentration of products is greater than the concentration of products
What does it mean if the equilibrium lies to the left?
It means that the concentration of reactants are gretaer than the concentration of products
What does the position of the equilibrium depend on?
Temprature
Pressure (only effects in gases
Concentration