Rates of Reaction & Equilibria Flashcards
what is rate
Rate = the speed at which something is happening
what would the equation for rate be for any reaction (2)
rate = the amount of reactant used up/time
OR
rate = the amount of product produced/time
‘the amount’ can be concentration, volume, mass
what is collision theory
The collision theory:
A reaction can only happen if the particle collides with a minimum amount of energy
what is activation energy
Activation energy = the minimum amount of energy required for a reaction to occur
what is it called when particles collide with energy greater or equal to the activation energy
When particles collide with energy greater or equal to the activation energy, these are called successful collisions
what is the rate of successfull collisions directly proportional to
The rate of successful collisions is directly proportional to the rate of collisions
what is the shape of a normal rate of reaction graph and why
A normal rate of reaction graph is a curve, where it increases and then plateaus
The reason for this shape is as the reactants get used up, the rate of collisions gets lower, so the rate of reaction slows down
how does temperature affect rate of reaction
High temperature can increase the rate of reaction as the particles will collide more due to more kinetic energy, this will cause collisions with more force and frequency, increasing the rate of successful collisions
how does pressure affect rate of reaction
High pressure can also increase the rate of reaction as more pressure will equal to more frequent collisions between particles, this is because higher pressure equals a higher amount of particles within an area, increasing the rate of successful collisions
how do catalyts affect rate of reaction
Catalyst can increase the rate of reactions as the definition of a catalyst is a chemical which speeds up reactions without being used up. Catalysts work by lowering the activation energy. This allows particles to collide with sufficient energy for successful collisions to take place.
how does concentration affect rate of reaction
A higher concentration increases the rate of reaction as there is a higher amount of particles in a volume, this would increase the frequency of the particles colliding with each other.
what do bombardier beetles defend themselves with
Bombardier beetles defend themselves by spraying a hot unpleasant liquid at their attackers
what makes the bombardier defensive liquid so hot
What makes the liquid hot is that they use an enzyme catalase which breaks down hydrogen peroxide into water and oxygen - this breakdown reaction occurs almost explosively, releasing a lot of heat
what can catalase be found in
This enzyme can be found in potatoes and liver tissues
how are catalysts written in reaction formulas
Catalysts aren’t written in reactions as they are present throughout and remain unchanged, so you can write them above the arrow
how do catalysts work
Catalysts work by providing an alternative route for the reaction, lowering the activation energy
how are catalysts useful in industry
Catalysts are really useful in industry as they help reactions occur faster, at lower temperatures and pressures than would otherwise be needed
THIS SAVES MONEY as high temperatures and high pressures both require a lot of energy.
what are reversible reactions
Reversible reactions = where reactions can take place in both directions
A reversible reaction is indicated using the special arrow
where can dynamic equilibrium happen
In a sealed container, a reversible reaction can reach dynamic equilibrium
For a reaction at dynamic equilibrium:
what needs to happen for a reaction to reach dynamic equilibrium (2)
- the forward and backward/reverse reactions occur at the same rate
- the concentration of reactants and products remain constant
what is an example of a reversible reaction
copper sulfate, hydrous becoming anhydrous through heating
what are the chemical formula for the reactions for copper sulfate heating
CuSO4.5H20 –> CuSO4 + 5H2O
AND
CuSO4 + 5H20 –> CuSO4.5H20
give another example of a reversible reaction including an Ammonium salt
NH4Cl –> NH3 + HCl
what is a sealed container / closed system (2)
A sealed container is when no substances are added to a reaction nor do they escape.
HOWEVER heat can be absorbed or released.
what is le chateliers principle
Le Chatelier’s Principle = when a change is made in a sealed container, the equilibrium shifts to counteract the change
what needs to be for pressure to affect equilibrium
For pressure to affect equilibrium, the total number of gaseous elements on both sides needs to be different.
what is pressure
Pressure is caused by the force exerted on the walls of the container by gas particles colliding into the walls
Particles colliding into each other does NOT contribute to pressure
what happens to equilbrium if you increase pressure and why
If you INCREASE the pressure, equilibrium is going to shift to try to DECREASE the pressure
In order to decrease the pressure, equilibrium is going to favour the side that produces a LOWER amount of gas molecules
This is because, by trying to reduce the amount of gas molecules, it can reduce the pressure
what happens to equilibria in the reaction N2 + 3H2 -> 2NH3 when the ammount of gas molecules is different on each side
With the reaction to make ammonia, to make as much ammonia as possible, you want to increase the pressure so that equilibrium shifts to the right.
If you increase pressure, equilibrium will shift to the side with less total gas molecules, and vice versa.
where does equilibrium shift in a reaction
equilbrium will shift to the direction the arrow is pointing in for the favoured reaction
what is enthalpy change shown for in a reversible reaction
For a reversible reaction, the enthalpy change shown is for the forward reaction
The symbol of the enthalpy change is the opposite for the reverse reaction, but the value stays the same
If the forward reaction has an enthalpy change of -150 what will the backwards reaction change enthalpy be
If the forward reaction has an enthalpy change of -150, the backward/reverse reaction will have a change of +150 (for enthalpy change you always have to include the sign)
what enthapy +- do exo and endo hav e
Exothermic reactions have a -ve enthalpy, endo has positive
does temperature change a dynamic equilibrium
At dynamic equilibrium, the rate of the forward and reverse reactions are equal
So, at dynamic equilibrium, the temperature of the sealed container does not change, as both reactions occur at the same rate, so the same amount of energy is being released, that is taken in
what happens to equilibrium when you increase the temperature
If you increase the temperature, equilibrium will want to decrease the temperature. So, equilibrium will favour the endothermic reaction, so equilibrium will shift to the appropriate side - and vice versa
what happens to equilibrium when you decrease the temperature
If you decrease the temperature, equilibrium will want to increase the temperature so it will favour the exothermic reaction, equilibrium will shift to the appropriate side
when does equilibrium shift to endo/exo (2)
When you increase temperature, equilibrium shifts in the endothermic direction
When you decrease the temperature, equilibrium shifts in the exothermic direction
does a catalyst affect equilibrium and why
The use of catalysts have no effect on equilibrium This is because a catalyst speeds up BOTH reactions (forward AND reverse) by the same proportion
what is the purpose of adding a catalyst in terms of equilibrium
The purpose of adding a catalyst is to speed up the rate at which equilibrium is reached
what is NO2 and its colour
dark brown poisonous gas
