C6: Reversible Reactions Flashcards
What is a reversible reaction?
A reaction that can go backwards - the products can react to form the reactants.
How do reversible reactions reach equilibrium?
1) As reactants react, concentration falls - so forward reaction will slow down. But as more products are made the backward reaction speeds up.
2) Over time the forward reaction will be going at same rate as the backward - system is at an equilibrium.
3) both reactions are still happening but with no overall effect (a dynamic equilibrium) - concentrations of reactants and products are balanced and won’t change.
4) Only reaches of the RR takes place in a ‘closed system’ (none of the products or reactants can escape & nothing can get in).
When a reaction is at equilibrium, does it mean the amounts of reactants and products are equal?
No; if the equilibrium lies to the right, the concentration of products is greater and the opposite when it lies to the right.
What conditions does the position of equilibrium depend on?
Temperature
Pressure (only involving gases)
Concentration of reactants and products
Explain what happens when the temperature is changed.
If it’s endothermic one way, it’s exothermic the other. So if you decrease the temperature, the equilibrium will move in the exothermic direction to produce more heat. Meaning you’ll get more products for the exo. reaction and less for the endo. And so on the other way round.
What is Le Chatelier’s Principle?
If you change the conditions of a RR at equilibrium, the system will try to counteract that change.
It can be used to predict the effect of any changes you make to a reaction system.
When looking at the effects of gas, what must you check?
The number of particles in each side / which side has higher pressure
What happens when there’s a change in pressure?
(Can only affect an equilibrium involving gases)
If you increase the pressure. It moves in the direction where there are deer molecules of gas (to try and reduce it). The same for the other way around.
What happens if the concentration is changed?
If you decrease the concentration of the products the system tries to increase it again by reducing the amount of reactants. And so on for the other way around.
