Topic G: Chemical Equilibrium Flashcards
What is dynamic equilibrium
When the rates of the forward and reverse reaction are equal. The reaction has not stopped, just that forward and backward reactions are occurring at the same rate
The concentration of all the reactants and products remain constant if the temperature is kept constant
How is it shown on a graph when dynamic equilibrium is reached
For concentration-time graph, it is when the concentration of the reactants becomes constant
For rate-time graph, it is when the rate of both forward and backward reactions become equal
What is homogenous chemical equilibrium
Systems where the reactants and products are in the same physical states
What is heterogenous equilibrium
It occurs when one or more of the reactants or products is in a different phase to the other reactants or products
Why do solids not appear in the formula for equilibrium constant
Solids do not have concentrations
Why does the concentration of pure solids or liquids not appear in the expression for equilibrium constant
The concentration of a pure solid or a pure liquid is similar to its density, which remains almost constant at any temperature
What do the different values of K tell us about a reaction
If K «_space;1: Reaction has hardly proceeded
If K < 1: Equilibrium lies towards reactants and the mixture contains mainly the reactants
If K = 1: Both reactants and products at equilibrium
If K > 1: Equilibrium lies towards products and the mixture contains mainly the products
If K»_space; 1: Reaction goes almost to completion
What is the value of K dependent and not dependent on
The value of K is only temperature dependent
It is not dependent by:
- Change in concentration of reactants or products
- Change in the pressure of the system
- The presence of a catalyst
What is Le Chatelier’s Principal
If a change is made to the conditions of a system at dynamic equilibrium, then the position of equilibrium will shift to counteract the change and establish a new equilibrium
What happens if some reactants is added to a reaction at equilibrium
The forward reaction works to remove excess reactant added and POE shifts from left to right
Reactants react to produce more products
At the new equilibrium, there will be more products but less of the other reactant
What happens if some reactants is removed from a reaction at equilibrium
The reverse reaction works to replace the removed reactant and the POE shifts from right to left
Products react to produce more reactants
At the new equilibrium, there is less products but more of the other reactant
What happens if the pressure of a system in equilibrium is increased
This causes the POE to move in the direction that results in a decrease in the total number of moles of gaseous particles
What happens if the pressure of a system in equilibrium is decreased
This causes the POE to move in the direction that results in an increase in the total number of moles of gaseous particles
What happens if there is an increase in reaction temperature to a reaction at equilibrium
The POE shifts to favour the endothermic reaction to remove some heat energy
K changes
What happens if there is a decrease in reaction temperature to a reaction at equilibrium
The POE shifts to favour the exothermic reaction to produce some heat energy
K changes