Topic 10: Chemical Equilibrium

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  • Created by: LouiseG
  • Created on: 27-04-16 09:24
What are the two conditions for chemical dynamic equilibrium to be established?
The reaction must be reversible, and must occur in a closed system (e.g. a sealed vessel).
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What defines a system in dynamic equilibrium?
The rate of the forward reaction is equal to the rate of the backwards reaction. The net concentration of products and reactions is constant. Both forward and back reactions continually happen.(Concentrations aren't necessarily the same:i.e. not 1:1)
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What will happen if you increase the concentration of a reagent in a system in equilibrium?
The equilibrium will shift to produce more of the product to oppose the change. If one substance is removed (e.g. a gas escaping) the equilibrium will shift to produce more to replace it.
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What will happen if pressure is increased on this reaction: 2A(s) + 3B(g) --> 4C(g)
The equilibrium would shift to the left (favour the reagents more). This is as an increase in pressure will cause a shift to the side with fewer moles of molecules - in the GAS phase (disregard the solid).
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If a forward reaction (which produces a desirable product) has a -ve enthalpy, what change in conditions would produce more product?
A lower temperature. This is as -ve enthalpy means an exothermic (heat-releasing reaction) so decreasing the temperature will favour the reaction that warms the system back up again.
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What affect does adding iron trays have on the production of ammonia?
None on the yield (equilibrium isn't affected by catalysts) but it will increase the rate (i.e. the speed at which the product is formed and equilibrium reached).
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A mixture of 2NO2 (g) -> N2O4 (g) (forward -ve) is heated. Why is it difficult to predict the change in equilibrium?
An increase in temperature favours the backward reaction (the endothermic direction). However, a temperature increase increases pressure, which would shift the equilibrium to the right. Thus it is hard to determine which factor is more significant.
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What is a homogenous system?
One where all the components are in the same phase.
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How is Kc written?
aA + bB --> cC + dD is ( [C]^c * [D]^d) / ( [A]^a * [B]^b )
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What is ommited from Kc?
Any components in the liquid or solid phase as their concentrations do not change.
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Thus what would Kc be for: CaCO3 (s) --> CaO(s) + CO2 (g)
[CO2]
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What are "compromise conditions"?
Where, in industry, an informed balance is found between costs, yield and rate.
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Why are very high pressures not used for the Haber Process?
Although it would increase yields, it would be expensive to maintain high pressures and expensive, resistant materials would need to be developed to contain it.
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Other cards in this set

Card 2

Front

What defines a system in dynamic equilibrium?

Back

The rate of the forward reaction is equal to the rate of the backwards reaction. The net concentration of products and reactions is constant. Both forward and back reactions continually happen.(Concentrations aren't necessarily the same:i.e. not 1:1)

Card 3

Front

What will happen if you increase the concentration of a reagent in a system in equilibrium?

Back

Preview of the front of card 3

Card 4

Front

What will happen if pressure is increased on this reaction: 2A(s) + 3B(g) --> 4C(g)

Back

Preview of the front of card 4

Card 5

Front

If a forward reaction (which produces a desirable product) has a -ve enthalpy, what change in conditions would produce more product?

Back

Preview of the front of card 5
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