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0620 Chemistry Processes Cheat Sheet (DRAFT) by

all processes in igcse 0620 chemistry

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Haber Process

For
• Industrial manufa­cture of ammonia
Raw materials
• Nitrogen (fract­ional distil­lation of liquid air)
• Hydrogen (cracking of hydroc­arbons)
Conditions
• Temper­ature: 450°C
→ Low temper­ature since reaction is exothermic
• Pressure: 200 to 300 atm
→ Favours side with lower gaseous moles (products side)
• Catalyst: Iron granules
→ Granules used as they have high surface area, which helps speed up reaction (save time)
• N₂ and H₂ are contin­uously added in 1:3
→ Increases concen­tra­tion, shifting equili­brium position to the right (incre­asing yield)
• NH₃ is contin­uously collected
→ Decreasing concen­tration of products shifts equili­brium position to the right (incre­asing yeild)
Reaction
N₂₍₉₎ + H₂₍₉₎ → 2NH₃ (ΔH= negative, exothe­rmic)
+ Using higher temper­ature will reduce yield of NH₃
+ Using lower temper­ature will slow down the rate of reaction too much.
+ Using higher pressure will make the process too expensive
+ Using lower pressure will reduce yield of NH₃

Contact process

For
• Manufa­cture of sulfuric acid
Raw materials
• Oxygen (from air)
• Sulfur
Conditions
• Temper­ature: 450°C (low temper­ature)
→ Reactions is exothermic thus, shifting equili­brium position to the left (higher temper­ature means lower yield and lower temper­ature means )
• Pressure: 2 atm (high pressure)
→ Increase in pressure shifts equili­brium position to the right (lower gaseous moles present there)
• Catalyst: V₂O₅
→ To increase rate of reaction
Reaction
• S + O₂ → SO₂ (oxida­tio­n/c­omb­ustion of sulfur)
• 2SO₂ + O₂ ⇌ 2SO₃ (oxida­tio­n/c­omb­ustion of SO₂ to SO₃)
• SO₃ + H₂SO₄ → H₂S₂O₇ (sulfur trioxide absorbed to H₂SO₄ to produce oleum)
• H₂S₂O₇ + H₂O → 2H₂SO₄ (oleum added to water to make H₂SO₄)
Purifi­cation of gases
• Takes place after SO₂ is made to purify SO₂ and O₂
→ Gases are passed through an electr­ostatic dust precip­itator to remove insoluble impurities such as sand
→ Gases are passed through a scrubber to remove water soluble impurities
→ Gases are passed through a drying tower to remove moisture
→ Gases are passed through an arsenic purifier to remove arsenic impurities
+ Lower temper­ature not used, rate of reaction will be too slow
+ Low pressure favors side with more gaseous moles (reactants side in this reaction)
+ Conditions such as adding the reactants and removing the product contin­uously are not mentioned as they don't affect the yield signif­icantly
+ Trioxide is not absorbed into water because it produces a fine mist of sulfuric acid which is difficult to condense and highly dangerous