12 - Reversible Reactions & Equilibria Flashcards
What are reversible reactions?
A chemical reaction that can work in both directions
How can the direction of some reversible reactions be altered?
By changing the reaction conditions
What symbol can be used to show that both forward & backward reactions happen at the same time?
What is meant by dynamic equilibrium?
- Rate of forward & backward reactions are the same
- Concentration of reacting substances stay the same
Why would dynamic equilibrium not be achievable in an open system?
Gases could escape so equilibrium would not be acheived
Why can dynamic equilibrium only occur in closed systems?
There is no loss of reactants or products so equilibrium can be achieved
What does the manufacture of ammonia by the Haber process involve?
A reversible reaction between nitrogen & hydrogen that can reach a dynamic equilibrium
Where is nitrogen obtained from for the Haber process?
The air
Where is hydrogen obtained from for the Haber process?
Natural gas or other sources
Which direction is the Haber process used to favour?
And explain why
Forward
—> To make a large amount of product as cheaply as possible
What are the conditions needed for the Haber process?
- 450 degrees Celsius
- Pressure of 200 atmospheres
- Iron Catalyst
What is the word equation for the Haber process?
How can the equilibrium position be altered?
And give some examples
By changing the reaction conditions (e.g. temperature, pressure & concentration)
What is the effect of changing INCREASING pressure in a reversible reaction?
In gaseous reactions, an INCREASE in pressure will favour the side with the FEWEST molecules
What is the effect of changing DECREASING pressure in a reversible reaction?
In gaseous reactions, an DECREASE in pressure will favour the side with the MOST molecules
What is the effect of changing INCREASING concentration in a reversible reaction?
Position moves AWAY from that reactant
What is the effect of changing DECREASING concentration in a reversible reaction?
Position moves TOWARDS from that reactant
What is the effect of INCREASING temperature in a reversible reaction?
Position moves in the direction of the ENDOTHERMIC reaction
What is the effect of DECREASING temperature in a reversible reaction?
Position moves in the direction of the EXOTHERMIC reaction
What happens to a change in the conditions made in a system that is already at equilibrium?
The system responds to counteract the change to bring it back to equilibrium
How can the effects of changing conditions on a system be predicted?
Using Le Chatelier’s principle
What does the relative amounts of all reacting substances at equilibrium depend on?
The conditions of the reaction
