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

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. 350K 550K

Recap Dynamic Equilibrium and Le Chatelier’s Principle before you move on… Dynamics and Le Chatelier's Principle Video Recap

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 TedEd Video = manufacture of ammonia by direct synthesis from nitrogen and hydrogen N2(g) obtained from atmosphere H2(g) obtained by thermal cracking of hydrocarbons N2(g) + 3H2(g) ⇌ 2NH3(g) ; H = -93 kJ mole-1 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 In practice, the process carried out at 450C and 20000kPa in the presence of an iron catalyst

“Compromise” 450C and 20000kPa used because: Why not higher? Why not lower? Pressure Temperature Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems. Reduced costs (see opposite) but reduced yield and rate Increased rate but decreased yield and increased energy costs Reduced energy costs but decreased rate speeds up the reaction without the need to raise temperature or pressure too much. IRON catalyst  acceptable yield and rate with acceptable energy (including CO2 emissions), equipment and safety costs.

% AMMONIA in main reaction vessel HYDROGEN & NITROGEN IN hydrogen + nitrogen ammonia HYDROGEN NITROGEN AMMONIA UNUSED HYDROGEN & NITROGEN RECYCLED TEMPERATURE and PRESSURE of the reaction vessel can be controlled % YIELD = % AMMONIA in main reaction vessel Mixture cooled here. AMMONIA condenses LIQUID AMMONIA REMOVED

Uses of Ammonia UK annual production: ≈1.3 million tonnes World 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

The Contact Process: Production of sulphuric acid H2SO4 3 simple reactions: The combustion of sulphur to form sulphur dioxide; The oxidation of sulphur dioxide to sulphur trioxide: 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

Contact Process = process by which sulphur dioxide, SO2, is converted to sulphur trioxide, SO3, for conversion to sulphuric acid 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 because exothermic (d) HIGHER pressure because 3 mols  2 mols Sulphuric Acid and The Contact Process RSC Video

“Compromise” 450C and 200atm used because: Why not higher? Why not lower? Pressure Temperature Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems. Reduced costs (see opposite) but reduced yield and rate Increased rate but decreased yield and increased energy costs Reduced energy costs but decreased rate speeds up the reaction without the need to raise temperature or pressure too much. V2O5 (Vanadium (V) oxide) catalyst  acceptable yield and rate with acceptable energy (including CO2 emissions), equipment and safety costs

The importance of sulphuric acid Uses of sulphuric acid:

Equilibrium and Industry Complete the following table Haber Process Contact Process Reactions and Conditions Justification of Conditions Importance of the Process

Making Methanol Carbon monoxide is converted to methanol by reaction with hydrogen at 250°C and (5 to 10) x 106 Pa using copper catalyst CO(g) + 2H2(g) ⇌ CH3OH(g) ; H = -90kJ mole-1 CO + H2 mixture produced by reacting methane with steam = “syngas”  CH3OH(g) manufacture favoured by: (a) excess CO and / or H2 (b) removal of CH3OH (c) LOWER temperature because exothermic (d) HIGHER pressure because 3 mols  1 mol

Le Chatelier’s principle for optimizing production

“Compromise” 250C and (5 to 10) x 106 Pa used because: Why not higher? Why not lower? Pressure Temperature Increased yield and rate but add to costs – pumping energy, structural engineering and safety problems. Reduced costs (see opposite) but reduced yield and rate Increased rate but decreased yield and increased energy costs Reduced energy costs but decreased rate speeds up the reaction without the need to raise temperature or pressure too much. Copper catalyst  acceptable yield and rate with acceptable energy (including lower CO2 emissions) and safety costs

Solutions

Time to Practise Work through the question pack Answers are at the back

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