2. Topic outline….
Lesson 1- Investigating an equilibrium reaction.
Lesson 2- Determining the Kc for an equilibrium
reaction.
Lesson 3- I.C.E. I.C.E. baby!
Lesson 4- ‘Free energy’ ?!
3. Lesson 1- Investigating an equilibrium reaction.
Level 4: State what a colorimeter is.
Level 7: Explain your qualitative observations in this
investigation using Le Chatalier’s principle.
Level 5/6: Estimate a value for the [FeSCN2+ ](aq)
using your standard graph.
4. Aim: to determine the Kc of an
equilibrium reaction.
See method from Vernier (on scidrive)
5. Lesson 2- Determining the Kc for an equilibrium
reaction.
Level 4: State what I.C.E. stands for.
Level 7: Determine the Kc value for this
equilibrium reaction using your data.
Level 5/6: Apply the I.C.E. method to determine the
equilibrium concentrations of each species.
6. Results from lesson 1…
See data analysis section of your results sheet
from lesson 1.
* See homework questions for review of topic 7 (from Pearson)
7. Lesson 3- I.C.E. I.C.E. baby!
Level 4: Write the equilibrium expression for
a series of equilibrium reactions.
Level 7: Determine the equilibrium
concentration(s) of a species from the
Kc using algebraic manipulation.
Level 5/6: Use the I.C.E. method to determine the
equilibrium concentrations of each species in an
equilibrium reaction.
9. Team activity- Ice, Ice baby…!
• Randomised groups of 3 students.
• Team name.
• 5 icy questions…
• Winners get p.lumps ☺
10. I.C.E. Q.Type 1- Determining Kc from equilibrium
concentrations.
PCl3(g) Cl2(g) PCl5(g)
Initial (mol.dm-3)
Change (mol.dm-3)
Equilibrium(mol.dm-3)
From Pearson pg. 331/332
*NB- ensure you note the mole ratios of each species from the balanced equation!
Kc= 33!
11. I.C.E. Q.Type 1- Determining Kc from equilibrium
concentrations.
2NO O2 2NO2
Initial (mol.dm-3)
Change (mol.dm-3)
Equilibrium(mol.dm-3)
From Pearson pg. 332
*NB- ensure you note the mole ratios of each species from the balanced equation
AND the volume given in the question!
Kc= (0.10)2 / (0.20)2 x (0.25)= 1.0
12. I.C.E. Q.Type 2- Determining equilibrium
concentrations from the Kc constant.
From Pearson pg 333
18. Lesson 4- ‘Free energy’ ?!
Level 4: Define what Gibb’s free energy is in
relation to an equilibrium system.
Level 7: Show the relationship between ∆G0
and Kc.
Level 5/6:Interpret a graph of the relationship
between free energy (∆G0) and the position of
equilibrium.
19. Starter- Gibb’s free energy.
Josiah Willard Gibbs
∆G0 = ∆H - T∆S
The free energy (net energy) after you consider
the heat energy lost/gained from a chemical
reaction (∆H) and from the rearrangement of
atoms (∆S).
20. The position of equilibrium and free
energy (G).
1. The free energy will always drop as
an equilibrium reaction occurs.
2. The lowest possible energy state is
when equilibrium is reached.
3. If Gr > Gp (in a mixture) then there
is a loss of G (as it approaches
equilibrium) and so we say ∆G –ive
and the reaction makes lots of
product.
4. Spontaneous reaction
5. If Gr< Gp (starting with pure
products) then there would need to
be a gain in G to form product and
∆G +ive.
6. Non-spontaneous reaction
21. Relating this to Kc:
∆G0 = -RTlnK
∆G0 = -ive Spontaneous
rxn.
Favours products at
equilibrium
Kc >1
∆G0 = 0 At equilibrium [reactants]=[products] Kc= 1
∆G0 = +ive Non
spontaneous
rxn.
Favours reactants at
equilibrium
Kc<1
