The Equilibrium Constant Flashcards
What is Kc?
This is the equilibrium constant.
What happens when you have a homogeneous reaction that has reached dynamic equilibrium?
You can work out the equilibrium constant.
What is meant by a homogeneous reaction?
This is where all of the reactants and products are in the same physical state.
What is the general reaction?
aA+bB=dD+eE
What do the lower case letters stand for?
Moles of substance.
What does the upper case letters stand for?
Products/reactants
What do the square brackets stand for?
Concentration
What is concentration measured in?
mol dm-3
What is the express ion for Kc?
Kc= ([D]^d X [E]^e)/([A]^a X [B]^b)
How do you calculate Kc?
By putting numbers into the expressions.
Are the units for Kc always the same?
No
How do you find the units for Kc?
Put the units in the expression instead of the number, then cancel out as much as possible.
What can you do with the value of Kc?
You can estimate the position of equilibrium.
What happens if the value of Kc is high?
The larger the value of Kc, the further to the right equilibrium lies. There are more products relative to the reactants.
What happens if the value of Kc is low?
The smaller the value of Kc, the further to the left equilibrium lies. There are more reactants relevant to the products.
How can you investigate the equilibrium position with changing temperature using NO2 and N2O4?
Place two sealed tubes containing the equilibrium mixture in water baths, one water bath should be warm and the other should be cool. Observe the colours of the mixtures.
What will happen to the tube in the warm water bath?
It will change to a darker brown colour as the endothermic reaction speeds up to absorb the extra heat, pushing equilibrium to the left.
What will happen to the tube in the cool water bath?
The solution will lose colour as the exothermic reaction speeds up to replace the heat, shifting the equilibrium to the right.
How can you investigate the equilibrium position with changing concentration?
Mix iron(111) nitrate with potassium thiocyanate to produce iron(111) thiocyanate.
What colour is iron(111)nitrate?
Yellow
What colour is potassium thiocyanate?
It is colourless.
What colour is iron(111) thiocyanate?
Blood red
What happens when more reactants are added to the experiment?
The forward reaction speeds up to produce more product.
What happens when more product is added?
The backward reaction speeds up so more reactants are created.
