Kinetics and Equilibria
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Particles in liquids and gases are always ____ and ____ with each other.
A reaction won't take place between two particles unless:
They collide in the right direction. They need to be facing each other the right way
They collide at least a certain minimum amount of kinetic energy
What is this called?
The minimum amount of kinetic energy particles need to react is called the _____ _____. The particles need this much energy to ___ the bonds to start the reaction.
Reaction with ___ activation energies happen pretty easily. But reaction with ___ activation energies don't. You need to give the particles extra ___ by _____ them.
What is this diagram called and state what happens at each number of the diagram
1 - Here the bonds within each particle are being stretched
2 - If the particles have enough energy, the bonds will break
3 - This is the energy barrier that the particles have to overcome
4 - The separate bits from each particle can't exist by themselves - so they form new bonds and release energy
Molecules in a gas don't all have the ___ amount of energy.
Name the diagram and what each letter represents.
1 - The curve starts at (0,0) because no molecules have 0 energy
2 - A few molecules are moving slowly
3 - Most molecules are moving at moderate speed so their energies are at this range
4 - Activation Energy
5 - Some molecules have more than the activation energy. These are the only ones that can react
Increasing the ______ or ______ makes reactions faster.
If you increase the temperature, the molecules will on average have more _____ _____ and will move _____.
So the greater proportion of molecules have energies greater than the ______ ______ and be able to _____. This changes the _____ of the Maxwell-Boltzmann distribution curve - pushing it to the ____.
- Activation energy
And because molecules are moving faster, they'll ____ more often - another reason why ____ temperatures make a reaction faster... and why ___ temperature increases can lead to ____ increases in reaction rates.
What other 3 things can affect the reaction rate?
- Surface area
Increasing the conc. of reactants in a _____ or the pressure of a ___ means the particles are ____ together on average. If they are ____ together, they'll _____ more often. More ____ mean more chances to react.
If one reactant is in a big lump, then most the particles won't collide with other reactants. You need to crush these lumps so that more of the particles can come in ____ with the other reactants. A ____particle size means a ____ surface area. This leads to a _____ reaction.
Catalysts are really useful. They _____ the activation energy by providing a ______ ____ for the bonds to be broken and remade. If the activation energy is ____, more particles will have enough _____ to react.
- Different way
Catalysts increases the ____ of a reaction by providing an ______ reaction pathway with a _____ activation energy. The catalyst is ______ unchanged at the end of the reaction.
Catalysts are great. They don't get ____ up in reactions, so you only need a _____ ___ of catalyst. catalyse a ____ amount of stuff. they do take part in reactions, but they are ___ at the end.
Homogeneous Catalysts work by forming _____
A homogeneous catalyst is in the _____ state as the reactants. So if the reactants are gases, the catalyst must be a ___ too. And if the reactants are aqueous (dissolved in water), the catalyst has to be ____ as well.
A homogenous catalyst ____ up reactions by forming one or more _____ compounds with the reactants. The products are then formed from the _____ compounds.
The activation energy needed to form the intermediates (and to form the products from the intermediates) is ____ than that needed to make the products directly from the reactants.
If a reaction is speeded up by a homogeneous catalyst, it's enthalpy profile will have ____ ____ on it.
The catalyst is ____ again and caries of catalysing the reaction
Another way to monitor the rate of reaction when a gas is produced is to stand the reactant vessel on a ____ - the mass will _____ as gas is evolved.
Not every reaction produces a gas, though. Some produce a _____ that clouds a solution. You can monitor this type of reaction....
What is the problem with this?
By measuring how quickly a marker becomes invisible through the cloudiness
That with this method the result's subjective - different people might not agree over the exact point when the mark 'disappears'. And it only works if the reactants you started with were transparent.
Reversible reactions can reach _____ equilibria.
In a reversible reaction, as the reactions get used up, the forward reaction _____ _____ - and as more product is formed, the reverse reaction ____ ___.
After a while, the forward reaction will be going at exactly the ____ rate as the backward reaction. This is called dynamic equilibrium.
A dynamic equilibrium can only happen in a ____ system. This means that...
Nothing gets in or out.
If you change the ____, ____ or _____ of a reversible reaction, you tend to alter the position of ______. This just means that you'll end up with different amounts of reactants and products at equilibrium.
If the position of equilibria moves to the left, you get more _____. If it moves more to the right, you get more _____.
Catalysts have _____ effect on the position of equilibrium. They can't increase ____ - but they do mean that equilibrium is reached ____.
If you increase the concentration of a reactant, the equilibrium tires to get rid of the extra reactant. It does this by making _____ _____. So the equilibrium shifted to the ____.
If you increase the conc. of the product, the equilibrium tries to remove the extra ____. This makes the reverse reaction go _____. So the equilibrium shifts to the ___.
Increasing the pressure shifts the equilibrium to the side with ___ gas molecules. This _____ the pressure.
Decreasing the pressure shifts the equilibrium to the side with ____ gas molecules. This ___ the pressure.
Increasing the temperature means adding ____.
The equilibrium shifts in the ______ direction to absorb this heat.
- Endothermic (Positive Delta H)
Decreasing the temperature ____ heat.
The equilibrium shifts in the ______ direction to try and replace the heat.
Exothermic (Negative Delta H)
If the forward reaction's endothermic, the reverse reaction will be ______, and vice versa.
Predicting the effect of changing conditions is really important for _____ that use _____ ______. This is because they want to make as much _____ products as possible as cheaply as possible.
- Reversible reactions
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