title: lesson 3 equilibrium and industry learning objectives: – review the equilibrium constant...
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Title: Lesson 3 Equilibrium and Industry
Learning Objectives:– Review the equilibrium constant experiment from the last
lesson
– Summarise the impact of equilibrium effects on the Haber Process and the Contact Process
– Practise equilibrium exam questions
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Recap The diagrams below represent equilibrium
mixtures for the reaction Y + X2 XY + X at 350 K and 550 K respectively. Deduce and explain whether the reaction is exothermic or endothermic.
Y =
5 5 0 K3 5 0 KX = 350K 550K
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Recap Dynamic Equilibrium and Le Chatelier’s Principle before you move on…
Dynamics and Le Chatelier's Principle Video Recap
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This lesson…You will be covering Equilibrium and Industry…Industrial processes you have come across before in
IGCSE The Haber Process Sulphuric Acid and The Contact Process
Task for this lesson Read through the slides and watch the videos for ‘The
Haber Process’ and ‘The Contact Process’ Fill out the summary sheet for both reactions Read through the slides on ‘Making Methanol’ Answer the questions on the sheet on Equilibrium and
Industry Complete the SL Equilibrium exam questions
Haber Process
N2(g) + 3H2(g) ⇌ 2NH3(g) ; H = -93 kJ mole-1
= manufacture of ammonia by direct synthesis from nitrogen and hydrogen
N2(g) obtained from atmosphere
H2(g) obtained by thermal cracking of hydrocarbons
In practice, the process carried out at 450C and 20000kPa in the presence of an iron catalyst
Le Chatelier’s Principle suggests NH3(g) production is
favoured by :(1) HIGH pressure since 4 mols 2 mols
(2) LOW temperature since forward reaction exothermic
(3) Removal of NH3 to pull equilibrium to the right and increase the yield
Haber Process TedEd Video
speeds up the reaction without the need to raise temperature or pressure too much.
Why not higher? Why not lower?
Pressure
TemperatureReduced energy costs but decreased rate
Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems.
IRON catalyst
“Compromise” 450C and 20000kPa used because:
Increased rate but decreased yield and increased energy costs
Reduced costs (see opposite) but reduced yield and rate
acceptable yield and rate with acceptable energy (including CO2 emissions), equipment and safety costs.
HYDROGEN NITROGEN AMMONIA
HYDROGEN & NITROGEN IN
UNUSED HYDROGEN & NITROGEN RECYCLED
hydrogen + nitrogen
ammonia
TEMPERATURE and PRESSURE of the reaction vessel can be controlled
Mixture cooled here. AMMONIA condenses
LIQUID AMMONIA REMOVED
% YIELD =
% AMMONIA in main reaction
vessel
Uses of Ammonia
UK annual production: ≈1.3 million tonnesWorld annual production: ≈140 million tonnes
1. Ammonia is reacted with an acid to form an ammonium salt
e.g. 2NH3(g) + H2SO4 (NH4)2SO4 = ammonium sulphate
Ammonium sulphate is an essential component of many fertilisers
The ammonia acts as base – accepts a proton from the acid – to form the ammonium ion, NH4
+
NH3 + H+ NH4+
2. Ammonia is also used to make nitric acid, HNO3
Nitric acid is an essential reagent for making useful materials such as :
1. POLYAMIDES such as nylon
2. EXPLOSIVES such as TNT and nitroglycerine
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The Contact Process: Production of sulphuric acid H2SO4
3 simple reactions:
(i) The combustion of sulphur to form sulphur dioxide;
(ii) The oxidation of sulphur dioxide to sulphur trioxide:
(iii) The combination of sulphur trioxide with water to form sulphuric acid.
Overall rate depends on step (ii). So we apply Le Chatelier’s principle to this step:
2SO2(g) + O2(g) ⇌ 2SO3(g) ; H = -196kJ mole-1
2SO2(g) + O2(g) ⇌ 2SO3(g) ; H = -196kJ mole-1
SO3(g) manufacture favoured by:
(a) excess SO2 and / or O2(b) removal of SO3
(c) LOWER temperature(d) HIGHER pressure
Contact Process
because exothermicbecause 3 mols 2 mols
= process by which sulphur dioxide, SO2, is converted to sulphur trioxide, SO3, for conversion to sulphuric acid
Sulphuric Acid and The Contact Process RSC Video
speeds up the reaction without the need to raise temperature or pressure too much.
Why not higher? Why not lower?
Pressure
TemperatureReduced energy costs but decreased rate
Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems.
V2O5 (Vanadium (V) oxide) catalyst
“Compromise” 450C and 200atm used because:
acceptable yield and rate with acceptable energy (including CO2 emissions), equipment and safety costs
Increased rate but decreased yield and increased energy costs
Reduced costs (see opposite) but reduced yield and rate
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The importance of sulphuric acid
Uses of sulphuric acid:
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Equilibrium and Industry Complete the following table
Haber Process Contact Process
Reactions and Conditions
Justification of Conditions
Importance of the Process
CO(g) + 2H2(g) ⇌ CH3OH(g) ; H = -90kJ mole-1
CH3OH(g) manufacture favoured by:
(a) excess CO and / or H2
(b) removal of CH3OH(c) LOWER temperature(d) HIGHER pressure
Making Methanol
because exothermicbecause 3 mols 1 mol
Carbon monoxide is converted to methanol by reaction with hydrogen at 250°C and (5 to 10) x 106 Pa using copper catalyst
CO + H2 mixture produced by reacting methane with steam
= “syngas”
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Le Chatelier’s principle for optimizing production
speeds up the reaction without the need to raise temperature or pressure too much.
Why not higher? Why not lower?
Pressure
TemperatureReduced energy costs but decreased rate
Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems.
Copper catalyst
“Compromise” 250C and (5 to 10) x 106 Pa used because:
acceptable yield and rate with acceptable energy (including lower CO2 emissions) and safety costs
Increased rate but decreased yield and increased energy costs
Reduced costs (see opposite) but reduced yield and rate
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Solutions
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Time to Practise
Work through the question pack
Answers are at the back
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Recap Many industrial processes take advantage of
equilibrium effects.
Two of the most important are: Haber process for making ammonia Contact process for making sulphuric acid