1. Write down everything you can think of about this reaction:
Nitrogen + Hydrogen ⇌ Ammonia
⇌ reaction is reversible
rate of forward reaction = rate of reverse reaction
exothermic in one direction endothermic in the other
energy absorbed in one direction is equal to energy released in the other
elements making compound
N2(g) + 3H2(g) ⇌ 2NH3(g) 1

2. 4.6 Chemical Equilibrium
Objective: to explain chemical equilibrium and how conditions affect it, using the example of the Haber Process.
Outcomes:
All: I can define the term chemical equilibrium (D/E)
Most: I can explain the Haber Process (C)
Some: I can determine the affects of changing conditions on reversible reactions (A/B)
Keywords: equilibrium, reversible, closed system, conditions, yield, catalyst
Homework: Haber Process worksheet
Due: Thursday 2 May 2 2 2 2 2 2

3. Use the graphs to write a definition of equilibrium.
What is equilibrium?
The below graphs show what happens to the reaction rate and amounts of reactants and products in a closed system.
Equilibrium
A closed system is where none of the reactants or products or energy can get out.
Use the graphs to write a definition of equilibrium.
I can define the term chemical equilibrium (D/E) 3 3

4. What is equilibrium? Equilibrium
The point in a reversible reaction where the forward and reverse rates of reaction are equal. Therefore the amounts of reactants and products remain the same.
Equilibrium
Demo this by getting a tray of balls and getting one student to take one out as the other puts one in.
Or talk about walking the wrong way on the escalator.
I can define the term chemical equilibrium (D/E) 4 4

5. Nitrogen + Hydrogen ⇌ Ammonia
The Haber Process
Nitrogen + Hydrogen ⇌ Ammonia
N2(g) + 3H2(g) ⇌ 2NH3(g)
Uses of Ammonia
- fertilisers
Use the diagram to draw a flow diagram for the process.
I can explain the Haber Process (C)

6. Nitrogen + Hydrogen ⇌ Ammonia
The Haber Process
Nitrogen + Hydrogen ⇌ Ammonia
N2(g) + 3H2(g) ⇌ 2NH3(g)
What is the main use of ammonia?
Made into
ammonium nitrate
FERTILISER
What can ammonia be use for?
Plants need nitrogen to grow. They cannot absorb it from the air. Nitrates in the soil are absorbed through the roots
I can explain the Haber Process (C)

7. Reversible Reactions and Conditions will shift to cancel out
The position of the equilibrium
will shift to cancel out
any change in conditions
This means the reaction can be shifted from one direction to the the other.
Conditions
CONCENTRATION
TEMPERATURE
PRESSURE
CATALYST
Ask why moving the reaction in one direction or the other could be useful.. inductry, creates more product.
What are the conditions that can be changed?
I can determine the affects of changing conditions on reversible reactions (A/B)

8. Reversible Reactions and Conditions
A(aq) + 2B(aq) ⇌ C(aq) + 3D(l) ENDO
What happens to the equilibrium if the concentration of B is increased?
It moves to the right to use up B and makes more products.
If the concentration of C is increased the equilibrium shifts to the _________ to the use up ___ and make makes more ___________.
Ask why moving the reaction in one direction or the other could be useful.. inductry, creates more product.
What are the conditions that can be changed?
LEFT C
REACTANTS
CONCENTRATION

9. Reversible Reactions and Conditions
[Co(H2O)6]2+ + 4Cl- ⇌ CoCl4 + 6H2O ENDO
hexaaquacobalt(II) + hydrochloric acid ⇌ cobalt chloride + water
blue
pink
If the temperature is decreased for a reaction which is endothermic in the forward direction, the equilibrium shifts to the ________ to ________ the temperature and make more _________
Demo cobalt and temp
LEFT
INCREASE
REACTANTS
TEMPERATURE

10. Reversible Reactions and Conditions
N2(g) + 3H2(g) ⇌ 2NH3(g) EXO
What are the optimum temperature conditions to increase yield in the Haber Process?
LOW TEMPERATURES
450°C
If the temperature is ___________ for a reaction which is exothermic in the forward direction, the equilibrium shifts to the _________ to ________ the temperature and make more _________.
DECREASED
Low temperatures would be cost effective but they are not conducive to high rates of reaction as the particles are moving too slowly so a higher temperature is used to provide a compromise.
RIGHT
INCREASE
PRODUCTS
TEMPERATURE

11. Reversible Reactions and Conditions
N2(g) + 3H2(g) ⇌ 2NH3(g) EXO 2 1 3
What are the optimum pressure conditions to increase yield in the Haber Process?
HIGH PRESSURES
How many molecules of GAS are on each side?
200atm
If the pressure is ___________ the equilibrium shifts to the _________ to the side with the least number of molecules and makes more _________.
INCREASED
RIGHT
High pressures although producing more product are not practical in industry as they require a lot of energy and also very strong machinery to withstand them and this is therefore expensive so a compromise is reached instead.
PRODUCTS
PRESSURE

12. Reversible Reactions and Conditions
Write down 4 key features of a catalyst.
A catalyst:
1. increases rate of reaction
2. is not used up in the reaction
3. lowers the activation energy
4. provides an alternate pathway for the reaction.
A catalyst does not affect the equilibrium as it has an equal effect on the rate of the forward and reverse reactions.
CATALYST

13. Reversible Reactions and Conditions
To help with yields and the compromise in temperature and pressure in the Haber Process a catalyst is added.
N2(g) + 3H2(g) ⇌ 2NH3(g) EXO
CATALYST
IRON
MEDIUM PRESSURES
200atm
MEDIUM TEMPERATURES
450°C
I can explain the Haber Process (C)

14. Q. Hydrogen for use in the Haber process can be produced by reacting methane with steam. The methane and steam mixture is passed over a nickel catalyst at 800°C and a pressure of 30 atmospheres. The equation for this reaction is:
CH4(g) + H2O(g) CO(g) + 3H2(g)
The forward reaction is endothermic.
ai What conditions of temperature would increase the yield of products for the forward reaction at equilibrium? Explain your answer. (2)
ii Suggest why a temperature of 800°C, not higher or lower, is used in the industrial process.[H] (2)
bi What conditions of pressure would increase the yield of products from the forward reaction at equilibrium? Explain your answer. (2)
ii Suggest one reason why a pressure of 30 atmospheres is used in the industrial process. [H] (1)

15. Answers
ai High temperature; forward reaction is endothermic or forward reaction takes in energy (allow heat). /2
ii Not higher because energy costs would be high(er) or apparatus would be more expensive or apparatus would need to withstand higher temperatures; not lower because rate of reaction would be slow(er) or catalyst would not work. /2
bi Low pressure; forward reaction produces more molecules (of gas) or more (gas) molecules on right side of equation. /2
ii Some pressure is needed to move gases through apparatus or to increase the rate of reaction. /1
I can determine the affects of changing conditions on reversible reactions (A/B)

16. 4.6 Chemical Equilibrium
Objective: to explain chemical equilibrium and how conditions affect it, using the example of the Haber Process.
Outcomes:
All: I can define the term chemical equilibrium (D/E)
Most: I can explain the Haber Process (C)
Some: I can determine the affects of changing conditions on reversible reactions (A/B)
Keywords: equilibrium, reversible, closed system, conditions, yield, catalyst
Homework: Haber Process worksheet
Due: Thursday 2 May 16 16 16 16 16 16