Chapter Six : Equilibrium Systems Flashcards
Equilibrium reaction
A reaction where a chemical equilibrium is reached. This is the state in which both reactants or products are present in concentrations that have no further tendency to change
Equilibrium constant
The value of the concentration fraction at equilibrium
Kc
When Kc>10^4 more reactants have been converted into products, equilibrium moves to the right
When Kc<10^-4 more products have been converted to reactants, equilibrium moves to the left
Equilibrium equation
aA+bB+cC<>zZ+yY
Kc= (Z)^z(Y)^y/(A)^a(B)^b(C)^c
When does equilibrium constant change
When temperature changes
Extent of a reaction
The degree to which reactants are converted into products
Reaction quotient (Q)
When Q=Kc the equation is at equilibrium
When Q>Kc a net backward reaction is occurring
When Q
Le Chateliers principle
ANy change that affects the position of an equilibrium causes that equilibrium to shift in such a way as to partially oppose the effect of that change
How might an equilibrium be disturbed
Adding or removing a substance
Changing volume (pressure)
Changing temperature
Why would Le Chateliers principle be used?
To maximise the yield of desired product
Produce desired chemical at acceptable rate
Balance the above variables against cost, safety
The Haber Process
Making ammonia has a slow rate of reaction but low yield but when the temp is increased the rate is faster but the yield is low to change this;
- Use a catalyst
- Compress the gases
- Separate ammonia from unreacted N and H so it can be recycled and reused
Equilibrium application to haemoglobin
When O2 conc is high in the lungs the Hb4/Hb4(O2)4 equilibrium shifted to the right
When O2 conc is low on the tissues the Hb4/Hb4(O2)4 is shifted to the left
Equilibrium application to CO poisoning
When CO enters lungs the CO takes position of O2 within
Adding O2 for treatment pushes the Hb and O2 reaction to the right to make more Hb4(O2)4
As haemoglobin is used up in first equation the second equation has less reactant, this forces reaction backwards so Hb4(CO)4 is forced into Hb4 and 4CO freeing up CO so that it can be decomposed
Effect of changin reaction on Kc
Reverse - 1/Kc
Multiply - Kc^2
Divide - Kc^1/2
