96796
Equilibria
- some chemical reactions are reversible meaning both
the forward and reverse reactions can take place eg
when blue hydrated copper sulfate crystals are heated
they form white anhydrous copper sulfate and water and
if water is added to white anhydrous copper sulfate then
blue hydrated copper sulfate can be re-formed
- when ammonia chloride is heated in an open boiling tube
some ammonia and hydrogen chloride react to re-form
ammonia choride but some escapes to the atmosphere
- Open system as substances can enter or leave
- Open system as substances can enter or leave
- The effect of conditions on
equilibria
- position of equilibrium is affected by changes like temp
and pressure ....if conditions change the position of
equilibrium moves to oppose the change
- changing conditions affects the position of an
equilibrium is useful .......... it means that we can
change the conditions to make more of the
substances we want to make
- Effect of temperature on the position of an equilibrium
- Effect of pressure on the position of an equilibrium
- In an equilibrium involving gases changes
in pressure will affect the position of the
equilibrium. More gas particles in a mixture
the greater the pressure
- in the dinitrogen tetroxide equilibrium there is
one gas molecule on the left for every two
gas molecules on the right. this means that
pressure increaseswith forward reaction and
decreases with the reverse reaction
- in the dinitrogen tetroxide equilibrium there is
one gas molecule on the left for every two
gas molecules on the right. this means that
pressure increaseswith forward reaction and
decreases with the reverse reaction
- If the pressure of a system at
equilibrium is increased the equilibrium
position will change to lower the
pressure . the equilibrium position
moves towards the side with the
fewest gas molecules
- If the pressure of a system at
equilibrium decreases the
equilibrium will move to increase the
pressure . the equilibrium position
moves towards the side with the
most gas particles
- In dinitrogen tetroxide equilibrium if the pressure is increased the equilibrium position moves
to the left : the side with fewer gas molecules and so lower pressure. Meaning there will be more
colourless N2O4 and less brown NO2 in the mixture which will become paler.
- If the pressure is decreased the equilibrium position moves to the right : the side with
more gas molecules and so higher pressure. Meaning there will be less colourless N2O4
and more brown NO2 in the mixture which will become darker
- If the pressure is decreased the equilibrium position moves to the right : the side with
more gas molecules and so higher pressure. Meaning there will be less colourless N2O4
and more brown NO2 in the mixture which will become darker
- In an equilibrium involving gases changes
in pressure will affect the position of the
equilibrium. More gas particles in a mixture
the greater the pressure
- In an equilibrium the reaction in one direction is exothermic and in the
other direction its endothermic...due to the law of conservation of
energy
- Exothermic release energy to surroundings which get hotter
.... Endothermic take in energy from the surroundings which
get colder
- eg ...decomposition of dinitrogen
tetroxide to form nitrogen dioxide is
endothermic whilst the reverse
reaction to form dinitrogen tetroxide
from nitrogen dioxide is exothermic
- eg ...decomposition of dinitrogen
tetroxide to form nitrogen dioxide is
endothermic whilst the reverse
reaction to form dinitrogen tetroxide
from nitrogen dioxide is exothermic
- Exothermic release energy to surroundings which get hotter
.... Endothermic take in energy from the surroundings which
get colder
- If temp is raised the position of equilibrium will move to oppose
the change eg take in energy.... endothermic reaction get cold
so the position of equilibrium moves in the direction of the
endothermic reaction.
- This means that the yield of the chemicals made in the endothermic
reaction increases and the yield of those made in the exothermic
decreases
- This means that the yield of the chemicals made in the endothermic
reaction increases and the yield of those made in the exothermic
decreases
- If temp is lowered the position of the equilibrium will move to
oppose the change eg to release energy... exothermic reaction
gets hot so the position of equilibrium moves in the direction of
the exothermic reactiom
- This means that the yield of the chemicals made in the
exothermic reaction increases whereas those made in the
endothermic reaction decreases
- This means that the yield of the chemicals made in the
exothermic reaction increases whereas those made in the
endothermic reaction decreases
- In dinitrogen tetroxide equilibrium raising the temp will move the position of the equilibrium futher to the right to favour the
endothermic reaction ( makes more brown NO2 and less colourless N2O4 so the equilibrium mixture gets darker
- If the temp is lowered the position of the equilibrium will move futher to the left to favour the exothermic reaction ( makes more colourless
N2O4 and less brown NO2 making the mixture paler in colour
- If the temp is lowered the position of the equilibrium will move futher to the left to favour the exothermic reaction ( makes more colourless
N2O4 and less brown NO2 making the mixture paler in colour
- Effect of pressure on the position of an equilibrium
- position of equilibrium is affected by changes like temp
and pressure ....if conditions change the position of
equilibrium moves to oppose the change
- ammonia and hydrogen chloride cant escape so they
will react to re-form ammonia chloride...after time the
rate at which the ammonia chloride decomposes
equals the rate at which ammonia and hydrogen
chloride recombine.
- closed system substances cannot enter or leave
- closed system substances cannot enter or leave
- When the rate of the forward reaction equals the
rate of the reverse reaction the system is in a
state of equilibrium
- when at equilibrium the forward and reverse
reaction take place at the same rate.. this means
that even though both reactions are happening
the amount of each substance in the equilibrium
remains the same
- when at equilibrium the forward and reverse
reaction take place at the same rate.. this means
that even though both reactions are happening
the amount of each substance in the equilibrium
remains the same
- the position of equilibrium can vary
- if the equilibrium position lies to the left it means
that at equilibrium there are more of the chemicals
on the left of the equation (reactants) than those on
the right
- eg...... the reaction between nitrogen and hydrogen to
form ammonia reaches a state of equilibrium that usually
lies to the left... this means there is more nitrogen and
hydrogen than ammonia in the equilibrium mixture
- If an equilibrium lies to the right it means there are
more of the chemicals on the right (products) than
those on the left of the equilibrium mixture
- eg...... the reaction between nitrogen and hydrogen to
form ammonia reaches a state of equilibrium that usually
lies to the left... this means there is more nitrogen and
hydrogen than ammonia in the equilibrium mixture
- if the equilibrium position lies to the left it means
that at equilibrium there are more of the chemicals
on the left of the equation (reactants) than those on
the right
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