10:Equilibrium
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What happens to equilibrium if you increase the temperature?
It will favour the endothermic reaction ->it will also speeden the rate for both forward and backward reaction
What happens to equilibrium if you increase the pressure?
It will favour the side with fewer particles - Only consider moles Example: The Haber Process N2(𝑔)+3H2(𝑔)⇌2NH3(𝑔) Reactants: 1 mole N₂ + 3 moles H₂ = 4 moles of gas. Products: 2 moles of gas (NH₃).
What happens to equilibrium if you increase the concentration of reactants?
It will favour the side with products
What happens to equilibrium if you add a catalyst?
Doesn’t affect equilibrium. Affects rate equilibrium is reached however
What is a homogenous system?
A system which all components are all in the same phase
What is a heterogenous system?
A system where at least two different phases are present
What does the equilibrium constant (Kc) indicate?
The position of equilibrium for a reversible reaction at a certain temperature
Given the equation is aA + bB ⇌ cC + dD, how do you calculate the rate constant (Kc)?
Kc = [C]^c [D]^d / [A]^a [B]^b [ ] is concentration Reactants are denominator Products are numerator
What is dynamic equilibrium?
When in a closed system the rate of forward reaction equals the rate of the backward reaction
What happens to equilibrium when you increase temperature?
The endothermic direction (+ΔH)
What happens to equilibrium when you decrease temperature?
Equilibrium favours the exothermic direction (-ΔH)
What is the equation for the Haber process?
N2 + 3H2 ⇌ 2NH3
What are the conditions for the Haber process?
450°C 200atm
Why must a compromise be chosen for low temperatures?
They produce a high yield for exothermic reactions but it is too slow
Why must a compromise be chosen for high pressure?
High yield but expensive and carried a safety issue
What does is mean Kc is more that one?
Equilibrium favours the products - there is a greater proportion of products in the mixture at equal compared to reactants (thus the forward direction is favoured)
What does is mean Kc is less that one?
This means equilibrium favours reactants - there is a greater proportion of reactants in the mixture at equilibrium compared to products (reverse direction is favoured)
How does Kc change when you increase the temperature on an endothermic reaction?
It increases the value of Kc
How does Kc change when you increase the temperature on an exothermic reaction?
It decreases the value of Kc
How does Kc change if you change concentration or pressure?
The value of Kc does not change
Why does the value of Kc not change when you change concentration or pressure?
The system shift equilibrium to restore the original Kc
How does catalyst change the value of Kc?
It doesn’t -> they just speed up how fast equilibrium is reached but doesn’t affect equilibrium position