Unit 3.4.2 - Equilibria Flashcards
What is the sign for a reversible reaction?
⇋
What happens to the speed of the forward and backward reaction after a reaction has started?
To begin with the forward reaction happens much faster but as the reactants get used up the forward reaction slows down, however as more products are formed the backward reaction begins to speed up, until they both happen at the same rate
What is a dynamic equilibrium?
Where the forward and backward reaction are happening at the same rate and the concentrations of the reactants and products isn’t changing
What are two conditions for a dynamic equilibrium to be maintained?
Closed system at a constant temperature
What does Kc stand for?
The equilibrium constant
What is Kc?
A quantitative value for the position of equilibrium at a given temperature
What is the general formula for Kc for this equation: aA + bB ⇋ cC + dD ?
What does [C] mean?
The concentration of C
What three things alter the position of equilibrium in a reversible reaction?
Temperature, pressure and concentrations used
Is the forward or backward reaction faster when the position of equilibrium moves to the left?
The backward reaction
If the forward reaction is faster which way has the position of equilibrium moved?
To the right
If the backward reaction is faster are more products or reactants formed?
Reactants
If more reactants are produced which was had the position of equilibrium moved?
To the left
If the forward reaction is faster are more products or reactants formed?
Products
If more products are formed which was has the position of equilibrium moved?
To the right
What is Le Chatelier’s principle?
When a closed system in dynamic equilibrium is disturbed, it responds in such a way as to oppose the change and restore the equilibrium
If a reaction is exothermic what happens to the position of equilibrium if you increase the temperature?
The system will seek to oppose the increase in temperature by favouring the endothermic reaction to try and reduce the temperature, this increases the backwards reaction shifting the position of equilibrium to the left and producing more reactants
If a reaction is endothermic what happens to the position of equilibrium if you increase the temperature?
The system will seek to oppose the increase in temperature by favouring the endothermic reaction to try and reduce the temperature, this increases the forwards reaction shifting the position of equilibrium to the right and producing more products
What affects Kc? And what doesn’t?
Temperature does but pressure and changing concentrations of things doesn’t
If by changing the temperature you form more products how does Kc change?
Kc will rise
What happens to the position of equilibrium if you increase the concentration of the the reactants in a reaction?
The equilibrium tries to get rid of the extra reactants by favouring the forward reaction shifting the position of equilibrium to the right producing more products
What happens to the position of equilibrium if you increase the concentration of the the products in a reaction?
The equilibrium tries to get rid of the extra products by favouring the backward reaction shifting the position of equilibrium to the left producing more reactants
If by changing the concentration of the products you form more reactants how does Kc change?
Kc remains unchanged
A + B ⇋ C, what happens to the position of equilibrium is you increase the pressure?
The system seeks to oppose the increase in pressure by favouring the side with the fewest moles, increasing the forward reaction and producing more products
If by changing the pressure you produce more reactants how does Kc change?
Kc remains unchanged
How do catalysts effect the position of equilibrium and Kc?
They have no effect because they increase the forward and backward reactions by the same rate and so the equilibrium position doesn’t move
