Reversible Reactions and Equilibrium Flashcards
What does equilibrium mean?
The relative quantities of reactants and products will reach a balance and stay there
What happens when a reversible reaction takes place in a closed system?
A state of equilibrium will always be reached
What is a reversible reaction?
One in which the products of the reaction can react with eachother and convert back into reactants
What does dynamic equilibrium mean?
It is when the reaction has reached equilibrium, but reactions are still taking place in both directions
What is le Chatelier’s Principle?
If the conditions of an equilibrium are changed, or stressed, the position of the equilibrium moves to oppose the change or stress
What are the ways to change the position of equilibrium?
1) Change the concentration of the products/reactants (add or remove products/reactants)
2) Change the pressure (ONLY for reactions involving gases)
3) Change the temperature
What happens if you make the reaction hotter/colder/raise the pressure/lower the pressure/add a chemical/remove a chemical?
Hotter - equilibrium moves to cool it
Colder - equilibrium moves to heat it
Raise pressure - equilibrium moves to lower the pressure
Lower pressure - equilibrium moves to raise the pressure
Add a chemical - equilibrium moves to remove this chemical
Remove a chemical - equilibrium moves to add this chemical
What colour is bromine water?
Yellow
What does the strength of the colour of bromine water depend on?
How many bromine molecules (Br2) there are in the solution
What happens when sodium hydroxide solution is added to bromine water and why does this happen?
The bromine water goes clear.
This is because when sodium hydroxide is added to bromine water, hydroxide ions are added to the solution, and they react with the hydrogen ions, therefore the hydrogen ions are removed from the reaction.
The equilibrium moves to make more hydrogen ions, and the position of equilibrium shifts to the RIGHT. This results in more products forming, (Br and OBr, as well as H) so more bromine ions are formed. The solution is colourless.
What is the equation for the reversible reaction that occurs for bromine water?
Br2 (aq) + H2O (l) —’ Br- (aq) + OBr- (aq) + H+ (aq)
‘—
What happens when acid is added to bromine water and sodium hydroxide?
The solution goes back to yellow.
This is because more hydrogen ions are added to the reaction. The equilibrium shifts to the LEFT (reactants) to remove the hydrogen ions. As a result of this, more bromine molecules are formed. Ten solution is yellow/orange.
What is a forwards reaction?
When the position of equilibrium moves to the RIGHT
What is a backwards reaction?
When the position of equilibrium moves to the LEFT
What is the test for ammonia?
It is alkaline, so it turns red litmus paper blue.
