Equilibrium Flashcards
Definition of equilibrium law
For the equilibrium aA + bB cC + dD
Kc = [C]c[D]d/[A]a[B]b
What are the units of Kc
Vary
What is inferred by Kc value greater than 1?
The reaction is product favoured, the products on the right predominate at equilibrium
What does Kc value lower than 1 mean?
Reaction is reactant-favoured, reactants on the left predominade at equilibrium
How does temp. change affect Kc?
When the forward reaction is exothermic, as temp. increases, Kc decreases.
When the forward reaction is endothermic, as temp. increases Kc also increases.
How does Kc change?
Only when temp. is altered
Characterisitcs of equation at equilibrium
Rates of forward and reverse reactions are equal
Closed system
Constant conc. of reactants and products
Reversible reaction
Equation for reaction between methane and steam to produce hydrogen
CH3 + H2O –> 3H2 + CO
A process that may be used in future to obtain hydrogen gas for the haber process
Electrolysis of water
Haber process: fewer mole of gas on right. Pressure is increased, explain in terms of Kc why the equilibrium yield of ammonia increases
Kc value does not change, increased pressure increases concentration terms on bottom of Kc expression more than the top. System is now no longer in equilibrium. Top of Kc expression increases and bottom decreases until Kc is reached
Reaction between ammonia and oxygen to form nitrogen monoxide
4NH3 + 5O2 –> 4NO + 6H2O
How does addition of a catalyst affect equilibrium?
No effect as it affects both forward and backwards reaction equally
What is meant by dynamic equilibrium?
The equilibrium that exists in a closed system where the rate of the forward reaction is equal to the reverse reaction
When can you just use moles rather than conc. in a Kc expression?
When volume cancels out because same number of products and reactants
Why could equilibrium constant be different to data book value?
Equilibrium had not been reached yet
