Chemical equilibrium Flashcards
What’s dynamic equilibria?
Is a system which involves a reversible reaction
what is a reversible reaction?
one which may proceed in another direction
What occurs during a reversible reaction (rate of reaction)?
- the rate of the forward reaction is fastest at the start
- the rate of the backwards reaction increases as the reaction progresses
What occurs during a reversible reaction (forward and reverse reactions)?
eventually, the rates of the forward and reverse reactions will be equal. A dynamic equilibrium is reached.
What are the main features of a dynamic equilibrium?
- both forward and backward reactions occur at equal rates
- a closed system is required.
- concentrations of reactants and products are constant
what does a closed system do?
this prevents the loss or gain of reagents that could disrupt the equilibrium
What conditions can affect the position of equilibrium?
- concentration
- pressure
- temperature
- amount of reactants and products
What is Le Chatelier’s principle?
When any factor which affects a dynamic equilibrium is changed, the position of equilibrium will shift. In order to minimise/oppose that change
How do you answer equilibria questions?
-which reaction is favoured
-why?
- conc: to minimise change
- temp: endo or exothermic reaction
- pressure: identify the side with the least moles
-which way did the equilibrium move
-composition: + or - reactants/products
What does the direction of equilibrium depend on in terms of concentration?
depends on whether the concentration of a reactant or product is changed.
The equilibrium will move to minimise what has changed.
How does increased reactant/ reduced product move the equilibrium position?
to the right
When does changing total pressure apply?
when gases are present (check the state symbols)
what does the direction of equilibrium depend on in total pressure changes?
depends on the number of gaseous moles on either side of the equation
what does the change of total pressure favour (increase/decrease) ?
- an increase in pressure favours the side with the least no. of moles
- a decrease in pressure favours the side with the most no. of moles
What does the changing of temperature depend on?
the sign of the forward reaction.
What happens to equilibrium when the temperature is increased?
the equilibrium will move to cool the reaction down
if the reverse endothermic reaction is favoured…?
the equilibrium position moves to the left
increasing temperature will favour
ENDOTHERMIC REACTION
decreasing temperature will favour
EXOTHERMIC REACTION
What is the Haber process?
used in the manufacture of ammonia, which is used to make fertilisers, explosives, nylon and nitric acid etc.
What is the equation for the haber process?
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
what position is needed for maximum yield (haber process)?
equilibrium must be shifted as far to the right hand side as possible
What temperature is needed for maximum yield and why (haber process)?
Low temp
- favours the forward exothermic reaction
- equilibrium moves to the right
What pressure is needed for maximum yield and why (haber process)?
High pressure
- less gaseous moles of products/less gaseous moles on the right
- equilibrium moves to the right
