10: Equilibrium I Flashcards
What is a reversible reaction?
Products break down into reactants
Mixture is present
What is an irreversible reaction?
All reactants turn into products
What is the formation of products called in equilibrium?
Forward reaction
“left to right”
What is the formation of the reactants called in equilibrium?
Backward reaction
“right to left”
What does dynamic equilibrium mean?
Dynamic - forward and backward reactions are constantly occurring, rates are equal
Equilibrium - no net change to amounts of reactant and product
What are all reversible reactions assumed to occur in?
A closed system
What is the term if more reactant is present at equilibrium?
Equilibrium lies to the left-hand side
What is the term if more product is present at equilibrium?
Equilibrium lies to the right-hand side
What is Le Chatelier’s principle?
When a change is applied to a system in dynamic equilibrium, the equilibrium shifts to oppose the change
What happens if the conc of the reactant is increased/ conc of product decreases?
Equilibrium shifts to the right
What happens if the conc of the reactant decreases / conc of product increases?
Equilibrium shifts to the left
How does increasing pressure affect a system in equilibrium ?
Equilibrium shifts to the side with fewer moles of gas
How does decreasing pressure affect a system in equilibrium ?
Equilibrium shifts to the side with most moles of gas
How is enthalpy related in reversible reactions?
Enthalpy value in forward reaction is equal and opposite to that of the backwards reaction
One is exothermic, the other endothermic
If the forward reaction is exothermic, what affect will increasing/decreasing the temperature have?
Increased - equilibrium shifts to the left
Decreased - equilibrium shifts to the right
If the forward reaction is endothermic, what affect will increasing/decreasing the temperature have?
Increased - equilibrium shifts to the right
Decreased - equilibrium shifts to the left
What is the main reaction in the Haber process?
N2 + 3 H2 -> 2 NH3
All gas
What is the enthalpy of the forward reaction of the Haber process?
-92 kJ/mol
Where are the reactants found for the Haber process?
Hydrogen - natural gas
Nitrogen - atmosphere
What are the conditions of the Haber process?
Nitrogen to hydrogen in 1:3 ratio ~400 C 200 atm Iron catalyst Unreacted reactants are recycled
What are the compromises of the conditions of the Haber process?
High yield of ammonia (shifts equilibrium)
Produces it quickly (decreases time to reach equilibrium)
Economic considerations
What does the temperature (~400C) in the Haber process do?
Low temp - as forward reaction is exothermic
Increases rate of reaction
Compromise - reduces yield of ammonia but decreases production time
What does the pressure (200 atm) in the Haber process do?
High pressure - favours forward reaction (more ammonia)
Compromise - not as high as possible as its expensive
What does the catalyst (iron) in the Haber process do?
No affect on equilibrium
Increases rate of reaction
What is a stoichiometric power?
Means number of molecules in the equation
Big number in front of molecule
What is Kc?
Equilibrium constant
At a given temperature
Only gases, aqueous
What is the Kc equation?
[C]^c x [D]^d
——————- = Kc
[A]^a x [B]^b
[A] [B} - product of conc of reactants
[C] [D] - product of conc of products
a b c d - number of molecules of each molecule
What does a large Kc mean?
Higher conc of products than reactants at equilibrium
What does a small Kc mean?
Higher conc of reactants than products at equilibrium
What does a Kc value = 1 mean?
Roughly equal quantities of products and reactants at equilibrium
