Facts In Books Flashcards
How does a catalyst work
They lower the activation energy as they provide an alternative pathway at a lower energy level so more successful collisions occur
^^ meaning they speed up reactions
What do catalysts do and not do
They speed up reactions but are not used up
What is the meaning of a reversible reaction
A reaction that can be changed back to its original form > the reaction can go in both directions
What is the collision theory
In a chemical reaction, reactant particles must collide and the colliding particles must have enough energy for the collision to be successful
Give 2 ways you can measure the rate of a reaction
Amount of reactant used up (divide) time
Or
Amount of product made (divide) time
What is the effect of temperature on rates
If increased the reactant particles move more quickly which means they have more energy and collisions happen more therefore the rate of reaction increases
What effect does a catalyst have on a rate of reaction
They lower the activation energy, providing a different pathway and a lower energy level so more successful collisions occur
What affect does the surface area have on rates of a reaction
The fate will increase as more particles are exposed to the other reactant and more collision will therefore happen
What is the effect of concentration/ pressure on rates of a reaction
More reactant particles in same volume so a greater chance for particles to collide and rate increased
What is the mass of a substances measured with
Balance
Volume of a gas is measured with?
Gas syringe or burette
What factored effect rates of a reaction
Temperature change Concentration of a dissolved reactant Pressure of a reacting gas Surface area is changed Catalysts
Whats the activation energy
The minimum energy needed for particles to react
What does an iron catalyst do
Makes ammonia from nitrogen and hydrogen
What’s a platinum catalyst effect
Making ammonia from nitrogen and hydrogen
What is bond breaking
An endothermic reaction because energy must be supplied to break existing bonds
What is bond formation
Exothermic reaction because energy is released when new bonds are formed
How can you calculate the overall energy change for a reaction
Using bond energies
What’s the equation for energy change
Energy if bond breaking - energy if bond making
How do you work out the amount of energy used in bond breaking
Adding up the bond energies of all the bonds in the reactants
How do you work out the amount of energy given out from bond making
Adding up the bond energies of all the bonds in all the products
Give some facts on ammonia
It breaks down when it is heated
It’s a colourless gas
What happens when ammonium chloride breaks down
It firms ammonia gas and hydrogen chloride gas
What is a closed system
When I ether reactants nor products can enter or leave
What is the position of equilibrium
When reversible reactions reach a balance point, where the amount of reactants and the amount of products formed remain constant
When is an equilibrium reached
When the forward and reverse reactions occur at the exactly same rate
What is le chateliers principle
To do with dynamic equilibrium
If a dynamic equilibrium is disturbed by changing the conditions, the reaction moves to conteract change
How is a does concentration change the position of equilibrium
If more of a reactant is added, the system would work by removing this reactant and making more of the products
How does temperature change the position of equilibrium
Decreasing the temp moves the position of E in the direction of the exothermic reaction
Increasing the temp moves the position of E in the endothermic direction
How does changing the pressure effect the post Position of equilibrium
Increasing the pressure moves the position of E to the suede with the least number of molecules
What happens if you add a catalyst to an equilibrium reaction
It reduces the time to reach equilibrium but doesn’t change the position of E
Why do particles need to smash into one another
So the bonds are broken and new substance is made
What happens if activation energy is low
Particles don’t need to collide with much energy to react
Meaning they’ll react as soon as they’re mixed
What does carbon dioxide produce during a reaction
Fizzing
What’s is the concentration
Amount of molecules dissolved in a volume of water
What can’t you do if two reactants are gases
And what the alternative thing to do
Increase the concentration
So you increase the pressure
How can the rate of reaction between marble chips and hydrochloride acid be changed
Changing the temperature and surface area of reactants
Why are powders like icing sugar flour and custard powder dangerous
They react very quickly as they have very large surface areas so they need to avoid naked flames
What are the pros of catalysts
Very small amounts can be used and they can be used again and again thus many industrial chemical reactions use them
What is a drawback if catalysts
They are very specific to what they can be used on
What are catalysts in living things called
Enzymes
Sometimes known as biological catalysts
Where do reactions stop
One or both of the reactants are used up
What is the reactant called that causes the reactions to stop
Limiting reactant
How to measure the rate of reaction on a graph on a fine point on the graph
Make a tangent (straight line) on the curve of where the point asked is
Then draw a right angles triangle and find the steepness of the tangent by dividing the height by the width
Thus = vol. gas collected (divided) time taken
To measure reactions rates what do you need to do
Observe the reaction at time intervals
see amount of gas released
Change in mass
The colour or appearance change
