1.6 - Equilibria and Redox Reactions Flashcards
What is dynamic equilibrium?
As the reactant gets used up, the forward reaction slows down - and as more product is formed, the reverse reaction speeds up. After a while, the forward reaction will be going at exactly the same rate as the backward reaction; the concentrations of the reactants and products will not be changing anymore so it appears that nothing is happening
What is a closed system?
Nothing can get in or out of the reaction
What two things are needed for dynamic equilibrium to happen?
A closed system and a constant temperature
What does changing the position of equilibrium mean?
This means that you’ll end up with different amounts of reactants and products at equilibrium
What is le Chatelier’s Principle?
If a reaction at equilibrium is subjected to change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change
Do catalysts change the position of equilibrium?
Catalysts have no effect on the position of equilibrium but they do make sure the equilibrium is reached faster
How does increasing the concentration of the reactant affect the position of equilibrium?
If you increase the concentration of a reactant, the equilibrium tries to get rid of the extra reactant by making more product - the equilibrium is shifted to the right
How does increasing the concentration of the product affect the position of equilibrium?
If you increase the concentration of the product, the equilibrium tries to remove this extra product, making the reverse reaction happen faster so the equilibrium shifts to the left
What state of matter does changing the pressure affect the position of equilibrium?
In gases
What happens to the position of equilibrium when you increase the pressure?
Increasing the pressure shifts the equilibrium to the side with fewer gas molecules
What happens to the position of equilibrium when you decrease the pressure?
Decreasing the pressure shifts the equilibrium to the side with more gas molecules
What happens to the position of equilibrium when the temperature increases?
The equilibrium shifts in the endothermic direction
What happens to the position of equilibrium when the temperature decreases?
The equilibrium shifts to the exothermic direction
What are compromised conditions?
Compromised conditions aim to make the most amount of product in the shortest amount of time
What is the equilibrium constant?
The equilibrium constant is the ratio worked out from the concentrations of the products and reactants after equilibrium is reached
What is the equation for Kc?
For a general reaction of aA + bB ⇌ dD + eE:
[D]^d [E]^e) / [A]^a [B]^b
What do the square brackets mean in regards to equilibrium?
Square brackets mean concentration in mol/dm3
How are equilibrium concentrations calculated?
1) Find out how many moles of each reactant and product there at equilibrium
2) Calculate the molar concentrations of each reactant and product by dividing each number of moles by the volume of the reaction. The volumes must be in dm3
How does Kc change if more product is formed?
Kc will rise if more products are formed
How does Kc change if less product is formed?
Kc will decrease if fewer products are formed
How does Kc change if the concentration changes?
Kc will stay the same
What is a loss of electrons called?
It is called oxidation
What is a gain of electrons called?
It is called reduction
What is a redox reaction?
A reaction where oxidation and reduction happen simultaneously
What does an oxidising agent do?
It accepts electrons and gets reduced
What does a reducing agent do?
It donates electrons and gets oxidised
What does the oxidation state of an element tell you?
It tells you the total number of electrons it has donated or accepted
What is the oxidation state of an uncombined element or a diatomic element?
0
What is the oxidation state of a simple monatomic ion?
It is the same as its charge
What are the oxidation states in compounds or compound ions?
Each constituent atom has an oxidation state of its own, and the sum of the oxidation states equals the overall oxidation state. This overall oxidation state is equal to the overall charge of the ion
What does the sum of the oxidation states in a neutral compound equal to?
It equals to 0
What is the anomaly with the combined oxygen in peroxides?
It’s oxidation state is -1 instead of -2
What is the anomaly with combined hydrogen in metal hydrides?
It’s oxidation state is -1 instead of -1
How can half-equations for oxidising and reducing agents be combined?
The electrons have to be the same on both sides for them to cancel out
How do you write half equations when the oxidising and reducing agents contain oxygen or hydrogen?
You add water or H+ ions on the side that its needed
