Chemistry- Unit 2- Equilibria

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  • Created by: FireDwarf
  • Created on: 31-01-14 19:43
What is equlibrium?
When the reactants are turning into products and products into reactants, in a reverisble reaction, at the same rate thus no change in the mass of the reactants or products.
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What rules/conitions about equalibrium? (4)
closed system, rates of both directions must the same same, posistion will be the same regardless of direction coming from, we will know its done when theres no changes in mass,conc etc.
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What is occuring in a+ b --> c + d
we have a quantity of a & b (reactants). These are turning fast into c & d, causing reaction to slow down. But c & d are turning back into a & b. Equalibrium when no further changes can be observed in a&b & c &d.
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why do we attempt to change the posistion of the equlibrium?
To increase product yield.
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Who came up with a principle regarding this?
Le chatelier (Principle)
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What is his principle?
If a system at equalibrium is distrubed, the equlibrium moves in the direction which reduces this disturbance.
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What happens when we change concentration, increase?
Increasing conc causes the equlibrium to move in the direction which reduces this concentration increase eg: increases a causes more b to be used, more products c & d and thus more to the right.
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Decrease?
Moves to the side which aims to increase the concentration.
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Changing pressure? Positive?
ONLY GASES. Moves in the direction which contains less molecules.
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Decrease?
Moves to the side which contains more molecules.
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How do we read the triangle H's? If the Triangle H is negative, what does this mean?
From left to right & negative indicates a exothermic reaction.
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Increase temperture?
Moves in the direction which cools it down which is endothermic.
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Decrease temperture?
Moves to side which increases temperture, exothermic.
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Catalysts?
NO EFFECT, THEY JUST INCREASE RATE OF REACTION.
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Two ways of producing ethanol? (words)
By fermentation of sugar & by fractional distilation & then cracking to produce ethene (then hydrating it).
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2 Equations?
C6H12O6 - 2C2H5OH + 2CO2 & C2H4 --> C2H5OH
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Uses?
Ethanol has many industrial uses, such as for making cosmetics, drugs, detergents, inks and a motor fuel.
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Temperture Conditions?
Low temperature because reaction is exothermic from reactants to products and a lower temperature favours the exothermic side, thus producing more products.
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Pressure? Conc of Steam?
: High pressure because fewer molecules on the right side.Excess steam concentration, increases products to reduce steam concentration.
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Limitations?
BUT… Lower temperatures reduce the rate of reactions but this is combated by use of catalyst. High pressure increases costs of equipment to sustain the pressure. Too much steam dilutes the catalyst.
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What is the formula for the Haber Proccess?
n2 + 3h2 --> 2nh3
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Uses?
. Ammonia is used to make fertilisers, explosives, dyes, household cleaners and nylon. It is also the most important raw material in the manufacture of nitric acid.
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Conditions?
The conditions used for the reactions are a high temperature - about 450ºC, a high pressure - about 200 atmospheres (200 times normal pressure) and an iron catalyst.
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What is the pressure & temperture?
A compromise. The temp is high to favour fast rate of reaction but low enough to create a high enough yield. Pressure is high to favour product yield while not too high due to expenses. Iron cataylst makes up for reduced rate of reaction.
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Methanol production equation?
C0 + 2H2 CH3OH
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Uses?
Used as a chemical feedstock; starting material for making other chemicals (eg: methanal which goes into making plastics). Methanol can also be used, when combined with other chemicals, to produce a motor fuel.
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Conditions?
Low temperature because the forward direction is exothermic. This means that a low temperature will favour this direction and thus increase yield of product. It also needs a high pressure because there is less molecules on the products side,
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Other cards in this set

Card 2

Front

What rules/conitions about equalibrium? (4)

Back

closed system, rates of both directions must the same same, posistion will be the same regardless of direction coming from, we will know its done when theres no changes in mass,conc etc.

Card 3

Front

What is occuring in a+ b --> c + d

Back

Preview of the front of card 3

Card 4

Front

why do we attempt to change the posistion of the equlibrium?

Back

Preview of the front of card 4

Card 5

Front

Who came up with a principle regarding this?

Back

Preview of the front of card 5
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