3(c) Reversible Reactions and Equilibria Flashcards
Examples of Reversible Reactions
- Dehydration of copper (II) sulfate
- Heating Ammonium chloride
Dehydration of Copper (II) sulfate crystals
When heated gently: turns into white powder = anhydrous copper sulfate (crystals lose their water of crystallisation)
ENDOTHERMIC
Add water to white solid -> turns blue again. Becomes warm
EXOTHERMIC
CuSO4.5H2O ⇌ CuSO4 + 5H20
Heating Ammonium Chloride
When heated: splits into colourless gases of ammonia + hydrogen chloride
ENDOTHERMIC
These gases react further up the tube and form white solid (ammonium chloride)
EXOTHERMIC
Reversible Reactions
Some reactions are reversible. WHen a reaction can go both ways (i.e. the reactant react to form products, and products react to form reactants)
⇌
Dynamic Equilibrium
The rate of forward reaction = the rate of backward reaction
Dynamic = the reactions are still continuing
Equilibrium = the concentrations of the reactants and products remain constant
Factors that can affect the position of equilibrium
- Temperature
- Pressure
Why does a catalyst not affect the position of equilibrium
Speeds up forward + backward reaction by same proportion
So no NET change
Effect of Temperature: Endothermic
An increase in temperature shifts the position of equilibrium in the direction of the endothermic reaction
Effect of Temperature: Exothermic
A decrease in temperature shifts the position of equilibrium in the direction of the exothermic reaction
What does the system try to do?
Minimise the change
Pressure
Caused by molecules colliding with the walls of the container
Increasing Pressure
Position of equilibrium shifts to the side with the fewer moles of gas
Decreasing Pressure
Position of equilibrium shifts to the side with more moles of gas
What happens when there are the same number of moles on either side of the reaction?
The pressure does not affect the position of equilibrium
