Chemical Synthesis

Haber process, contact process, production of ethanol via hydration of ethene and fermentation of glucose, and hydrogen fuel cells

Equation of the Haber Process

Nitrogen + hydrogen —> ammonia + heat

N_2(g) + 3H_2(g) <-> 2NH_3(g) + heat

Conditions of the Haber Process

Catalyst - iron

High pressure (200atm) - equilibrium shifts right due to less moles of gas

High temperature (500 degrees) - increases rate of rxn even though it favours the reverse rxn

Describe the Haber Process

Production of ammonia used for fertilisers - not very efficient (35% yield), exothermic reaction

Describe the Contact Process

3 step process to make sulfuric acid - very efficient (at specific conditions)

most produced industrialised chemical in the world

Conditions of Step 2 of the Contact Process

Catalyst - vanadium oxide

High temperature (450 degrees) - increases the rate of rxn despite favouring the reverse rxn

Lower pressure (2atm) - already at over 95% yield, so no point to spend money on lower pressure

Step 1 of Contact Process

Make sulfur dioxide

sulfur + oxygen —> sulfur dioxide

S_(s) + O_2(g) -> SO_2(g)

Step 2 of Contact Process

Convert sulfur dioxide to sulfur trioxide (step that is optimised)

sulfur dioxide + oxygen → sulfur trioxide

2SO_2(g) + O_2(g) <-> 2SO_3(g)

Step 3 of the Contact Process

Convert sulfur trioxide to sulfuric acid

SO_3(g) + H₂SO_4(l) -> H₂S₂O_7(l)
H₂S₂O_7(l) + H₂O_(l) -> 2H₂SO_4(l)

Production of ethanol via hydration of ethene

ethene + water —> ethanol

Conditions for the hydration of ethene

Phosphoric acid

Temperature of 300 degrees

60-70atm

Production of ethanol via fermentation of glucose

glucose + yeast catalyst —> ethanol + carbon dioxide

C₆H₁₂O₆ —> 2C₂H₅OH + 2CO₂

Fermentation of glucose pros

Ethanol produced by fermentation is a biofuel (produced from renewable resources)

Hydration of ethene cons

Only 5% of ethene is converted into ethanol each time it passes the catalyst, so the process is repeated many times

Describe a hydrogen fuel cell

Type of galvanic cell

2 types - acidic and alkaline

H2 is always oxidised and O2 is always reduced

H2O (water) is produced and removed

Electrons flow from anode to cathode

Example electrolyte in both acidic and alkaline hydrogen fuel cell

Acidic: H₃PO₄

Alkaline: KOH

What happens in an acidic hydrogen fuel cell? (what’s oxidised and reduced, where is water produced, where do the ions flow?)

H2 is oxidised

O2 is reduced using H+

Water is produced at the cathode

Ions flow from anode to cathode

What happens in an alkaline hydrogen fuel cell? (what’s oxidised and reduced, where is water produced, where do the ions flow?)

H2 is oxidised using OH-

O2 is reduced

Water is produced at the anode

Ions flow from cathode to anode