C2 - Rates of Reaction Flashcards
Where are catalysts used?
They are used in industrial chemical reactions where there isn’t much time
They are used in catalytic converters
What is a catalyst?
A substance that massively increases the rate of a reaction without being used up or changed
What are the 4 factors that can change the speed of a reaction?
Temperature, concentration, surface area and pressure
Why is a catalytic converter needed?
The harmful gases of carbon monoxide and nitrogen oxides are changed to the much less harmful carbon dioxide and nitrogen
What is the biggest problem with catalysts?
They are very specific
Only one type of catalyst will catalyse a specific reaction
What is the Haber process?
Iron is used as a catalyst to produce ammonia from nitrogen gas and hydrogen gas
How do catalysts work?
The catalyst particles collide with the reactant particles and lower the activation energy by providing an alternative route for the reaction
What is concentration?
It is the amount of molecules of the reactant dissolved in a given volume of water
How does concentration change the rate of reaction?
If the particles are more crowded (higher concentration) they are much more likely to collide so the reaction is faster
How does pressure affect the rate of reaction?
If we squash more gas into a smaller area, the molecules will be closer together meaning they are more likely to collide
What is pressure?
How much gas has been squashed into a given area
They have more pressure making the particles closer together
How does temperature affect the rate of reaction?
If there is a higher temperature, the particles will vibrate more giving them more energy
More energy means they move faster and are more likely to collide
How does surface area affect the rate of reaction?
If the surface area is larger, more of the reactant is exposed meaning the particles of the other reactant are more likely to collide with it
Give 2 ways in which we can measure the rate of a reaction
How fast the reactants are used up
How fast the products of the reaction are formed
What is collision theory?
The theory that substances react when the particles of the reactants collide, break apart and then re-form to create new substances
What are successful collisions?
Collisions that result in a chemical reaction
What is activation energy?
The amount of energy that needs to be put in to trigger the reaction
What are the 3 ways of measuring the rate of reaction?
Change in mass
Volume of gas given off
Precipitation
How do you measure rate of reaction with precipitation?
This is when the product of the reaction is a precipitate that clouds the solution
Observe a mark through the solution and measure how long it takes to disappear
The quicker the mark, the quicker the tst
What are the 2 problems with the precipitation rate of reaction experiment?
Different people might not agree on the exact point that the mark disappears
Only works for reactions where the initial solution is clear
How do you measure rate of reaction using change in mass?
If a reaction produces a gas, you can measure the rate of reaction by looking at the change in mass (gas is lost)
You measure the change in mass by using a balance and looking at how fast the mass goes down
What is the advantage and disadvantage of the change in mass experiment?
Very accurate because the mass balance is accurate
But the gas is released straight into the room
How do you measure the rate of reaction with the volume of gas given off?
You use a gas syringe to collect up the gas of the reaction
The more gas given off in a given time, the faster the reaction
What is the advantage and disadvantage of the volume of gas given off experiment?
The volume of gas measured is very accurate
If the reaction is too violent, you can blow the plunger out of the end of the syringe
