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41 Cards in this Set

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What must particles do to react?
They must collide in the right direction (facing the right way) and must collide with a minimum amount of Kinetic energy.
What is activation enthalpy?
The minimum amount of kinetic energy needed for particles to react.(The particles need energy to break the bonds at the start of a reaction)
Activation Energy
Why is an Enthalpy Profile Diagram shaped like this?
because the reactants need enough energy for the bonds to break (Activation Enthalpy) and then the new bonds formed release energy.
What does a Maxwell-Boltzmann distribution show?
the number of molecules in a gas with different kinetic energies
What happens of you increase the temperature of a reaction?
Particles on average will have a higher kinetic energy and will move faster so a greater proportion of molecules will have the activation energy and will be able to react.
Also they will be moving faster so they'll collide more often.
zoom zoom
How does increasing the temperature affect the shape of the Maxwell-Boltzmann distribution curve?
It pushes to the right
Same amount of molecules so same area
Apart from temperature what else speeds up the rate of reaction?
Increasing the concentration
Increasing pressure
Increasing surface area
Addition of a catalyst
4 things
How does increasing the concentration of the reactants speed up a reaction?
Increasing the concentration of the reactants in a solution means the particles are closer together on average. If they're closer, they'll collide for often. So more collisions means more chances to react. Also more molecules means more molecules on average with high enough activation energy.
How does increasing the surface area speed up a reaction?
If the reactants are in a big lump then most of the particles won't collide with other reactants. However if they are in smaller lumps you will have a larger surface area to volume ration so more particles will come in contact with the other reactants.
surface to volume ratio
How does adding a catalyst speed up a reaction?
They lower the activation enthalpy by providing a different way for the bonds to be broken and remade. If the activation enthalpy is lower, more particles will have enough enthalpy to react.
What is a homogeneous catalyst?
A homogeneous catalyst is one which is in the same state as the reactants.
How do homogeneous catalysts work?
A homogeneous catalyst speeds up reactions by forming one or more intermediate compounds with the reactants. The products are then formed from the intermediate compounds.
How does having intermediate compounds speed up a reaction?
The activation energy needed to form the intermediates (and to form the products from the intermediates) is lower than that needed to make the products directly from the reactants.
double bump
What is the shape of an energy profile of a homogeneous catalyst reaction?
Why are there two bumps on the Enthalpy Profile of a homogeneous Catalyst Reaction?
because there are intermediate bonds that which need to be formed
What do Reversible Reactions reach?
Dynamic Equilibrium
reactions that can work in both ways
How is dynamic equilibrium reached?
As the reactants get used up, the forward reaction slows down- as more product it formed the reverse reaction speeds up. After a bit the forward and backwards reactions will be going at the same rate.( the amounts of reactants and products will not change)
What must the reaction happen in for it to reach Dynamic equilibrium?
can only happen in a closed system
What does Le Chatelier's Principle state?
If there is a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change.
How do catalysts alter the position of equilibrium?
They dont
How does changing the concentration alter the equilibrium?
•If you INCREASE the concentration of REACTANTS the equilibrium tries to get rid of the extra reactants and does this by making more product. So the equilibrium shifts to the RIGHT
•Increasing the concentration of the product the equilibrium tries to remove extra product so the reverse reaction will go faster. so equilibrium shifts to the LEFT
How does altering the pressure effect equilibrium?
•Increasing the pressure shifts equilibrium to the side with the fewest gas moles to reduce the pressure.
•Decreasing the pressure shifts the equilibrium to the side with the most bass molecules to increase the pressure.
moly mole
How does altering the temperature effect equilibrium?
•Increasing the temperature (adding heat) will cause the equilibrium to shift in the endothermic (positive ∆H) direction to absorb this heat.
•Decreasing the temperature (removal of heat) causes the equilibrium to shift in the endothermic (negative ∆H) direction to try and replace the heat
If the forward reaction is endothermic then the reverse will be exothermic.
What is the percentages of different gasses in the lower atmosphere?
78% - Nitrogen
21% - Oxygen
1% - Argon
0.035% - Carbon Dioxide
(varying amounts of water vapor and other gases in tiny amounts)
It comes out to over 100% as the figures have been rounded off slightly.
What does ppm stand for?
and what is it used for?
Parts Per Million
Is a measure used when talking about really small percentages of gas in the atmosphere.
eg Xenon = 0.000009% of the atmosphere which is 0.9 ppm .
not penguin party manifesto!
Name the EM radiation in order from lowest energy to highest energy?
Radio waves, Micro-waves, Infrared, Viable light, Ultra-violet, X-rays and Gamma rays
Ruth meddles in very unusual eXpeditions galore! :'( that is so bad
What EM radiation does the sun (main 3) give out and why does it give out radiation?
Infrared, Visible light, Ultraviolet
because of the nuclear processes going on in its core
is very Unhelpful
How does UV/visible light effect molecules?
Electrons get excited to higher energy levels. Bonds may be broken. (free radicals may be formed)
How does Infrared radiation effect molecules?
The BONDS in the molecules absorb energy and vibrate more.
shake shake shake señora
How do microwaves effect molecules?
The molecules absorb energy and rotate more
Literally a microwave!
How do radio waves effect molecules?
The molecule absorbs energy and translates more (moves faster)
Voom voom
What effects the frequency of the vibrations of molecules?
The strength of the bond
The mass of the atom
What are free radicals?
Atoms with unpaired electrons that are usually highly reactive so consequentially have a very short half life.
Describe the greenhouse effect?
The sun emits UV, IR and visible light. The radiation from reaches the earths atmosphere most of the UV and IR is absorbed by the atmospheric gasses, while some is reflected back in to space by clouds.
Radiation that reaches the earth is absorbed causing it to heat up. The earths radiates energy back towards to space as IR (heat). Troposphere absorbs this radiation and re-emits it further causing the earth to heat up.
a lit of absorption and emitted stuff!
Is the greenhouse effect essential for life?
Yes cause other whose the earth would be 30° cooler.
What is it that we don't need (regarding the greenhouse effect)?
An ENHANCED Greenhouse effect
What are the main greenhouse gasses?
Water vapour. carbon dioxide and methane
three of them
What are greenhouse gasses?
A gas which their molecules absorb IR radiation to make the bonds in the molecule vibrate more.
This extra vibrational energy is passed on to other molecules in the air by collisions, giving the other molecules more kinetic energy and so overall raising the overall temperature.
What does the effect a molecules have of the green house effect depend on?
•How much radiation one molecule of the gas absorbs
•How much of that gas there is in the atmosphere
What is causing the enhanced greenhouse effect?
•burning fossil fules (increasing CO2)
•Chopping down trees (reducing photosynthesis -> increasing CO2)
•more cows (leading to an increase in methane)
What do Maxwell-Boltzmann distributions show?
How many molecules have the activation energy ( or higher) so are as to react.
something to do with energy