equilibria (chapter 8) Flashcards
definitions
reversible reaction
a reaction which can proceed both forward or backwards as per conditions applied.
dynamic equilibrium + conditions
it is established when the rate of the forward reaction equals the rate of the backward reaction.
conditions- reactions must be reversible
- the system must be closed because energy exchange in and out can take place but matter exchange in and out of a system cannot take place.
Le Chatelier’s principle
if a change is made to a system at equilibrium, the equilibrium shifts to oppose that change.
how is concentration affected when
(i) equilibrium shifts to right
(ii) equilibrium shifts to left
(i) concentration of products increases
(ii) concentration of reactants increases
what happens to equilibrium when:-
(i) concentration of reactants decreases
(ii) concentration of products decreases
(i) equilibrium shifts to left
(ii) equilibrium shifts to right
what happens when
(i) the temperature increases
(ii) the temperature decreases
(i) endothermic reaction proceeds
(ii) exothermic reaction proceeds
what happens to the equilibrium when
(i) pressure is decreased
(ii) pressure is increased
(i) equilibrium shifts to the side with more molecules
(ii) equilibrium shifts to the side with fewer moles
write the equation for haber’s process and enthalpy change of reaction
3H2 + N2 –> 2NH3
forward reaction is exothermic
enthalpy change = -92 KJmol-1
state conditions for haber’s process
- temperature of 450 C
- pressure of 200 atm
- iron used as catalyst
Explain why optimum temperature of 450 is used in Haber’s process?
we use a lower temperature as the forward reaction is exothermic. However, any lower temperature will make the rate of reaction too slow. Hence optimum temp of 450 is used.
Why do we used a pressure of 200 atm(high) in the Haber’s process?
We use a high pressure because fewer moles of gas are present on the product side. However, going any higher will increase the cost of maintenance and machinery.
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