Reverse reactions and equilibrium Flashcards
What is a reversible reaction?
Some chemical reaction can proceed in both forwards and backwards directions. We describe these reactions as reversible.
What does a reversible reaction look like?
A + B –> C + D
What do the reactants (A+B) combine to make?
They combine to give the products (C+D)
What do products (C+D) combine to make?
They combine to give the reactants (A+B)
If the forwards reaction (transfers energy from reactants to the environment) what type of reaction would the backwards reaction be?
Endothermic (transfers energy from environment to the reactants)
What is conserved during chemical reactions?
Energy
What is eventually reached when reversible reactions happen within a closed system?
A dynamic equilibrium
What is a closed system?
A system where reactants and products can neither be added not removed.
What happens at dynamic equilibrium?
The rates of the forwards and backwards reactions are equal.
Why is the equilibrium dynamic?
Both the forward and backward reactions are still taking place.
What doesn’t change at dynamic equilibrium?
The concentrations of reactants and products.
What do the conditions determine in a reaction as equilibrium?
The relative quantities of the different reactants and products
What does Le Chatelier’s principle say?
If any of the conditions of a reversible reaction at equilibrium are changed, the closed system will adapt to counteract whatever has changed.
What is Le Chatelier’s principle used to predict?
The outcome of changes imposed on a system at equilibrium.
What does changing the conditions in a reversible reaction affect?
The position of equilibrium
What does changing the temperature for a reaction at equilibrium do?
Takes the system out of equilibrium. The system will react to try and restore the equilibrium.
What will decreasing the temperature in a chemical reaction do to the position of equilibrium?
The position of equilibrium will shift in the exothermic direction.
- The amount of products generated by the exothermic reaction will increase.
- The amount of products generated by the endothermic reaction will decrease.
What will increasing the temperature in a chemical reaction do to the position of the equilibrium?
The position of equilibrium will shift in the endothermic direction.
- The amount of products generated by the endothermic reaction will increase.
- The amount of products generated by the exothermic reaction will decrease.
If the forward reaction of a reversible reaction is endothermic, what happens when the temperature is decreased?
The backward reaction is favoured.
What happens to the position of equilibrium if pressure is increased?
The position of equilibrium will shift to favour the reaction that produces the fewest gas molecules.
What happens to the position of equilibrium if pressure is decreased?
The position of equilibrium will shift towards the side of the reaction that produces the most gas molecules.
Pressure changes only affect reactions involving reactants in what state?
Gas
What will changing the concentration of any reactant or product do to the system?
Takes the system out of equilibrium so the system will react to try to restore the equilibrium.
What happens when we increase the concentration of a reactant? (to the equilibrium)
This will shift the position of equilibrium towards the products.
What happens when we increase the concentration of a product?
This will shift the position of the equilibrium towards the reactants.
What do we need to assess to predict the outcome of pressure change?
We must assess balanced equations to see how many gas molecules are on each side of the equation.
