The Haber and Contact Process.

IGCSE Chemistry.

Chemical equation for the reversible reaction in the Haber process

N2​(g)+3H2​(g)⇌2NH3​(g)

Raw materials and their sources for the Haber process

Nitrogen (N2N2​) obtained from the fractional distillation of liquid air, and Hydrogen (H2H2​) obtained from reacting methane (natural gas) with steam.

Essential reaction conditions for the Haber process

Temperature of 450 ∘C, pressure of 200 atm. and an iron (Fe) catalyst.

Reason for choosing 450∘C in the Haber process

The forward reaction is exothermic. A lower temperature favours a higher equilibrium yield of NH3(g). 450∘C is a compromise temperature giving an acceptable yield at a reasonable reaction rate.

Reason for choosing 200 atm pressure in the Haber process

The forward reaction produces fewer gas moles (2 moles vs 4moles). Higher pressure shifts equilibrium to the right and increases rate. 200atm provides high yield without the safety hazards and extreme equipment costs of higher pressures.

Separation and recycling of unreacted gases in the Haber process

The reaction mixture is cooled so that ammonia condenses into a liquid and is removed. Unreacted nitrogen (N2) and hydrogen (H2​) gases are recycled back into the reactor vessel

Raw materials used in the Contact process to manufacture sulfuric acid

Sulfur (or sulfide ores like zinc blende), air (to supply oxygen), and water.

Chemical equation for the key reversible step in the Contact process

2SO2​(g)+O2​(g)⇌2SO3​(g)

Essential reaction conditions for converting SO2(g) to SO3​(g) in the Contact process

Temperature of 450 ∘C pressure of 1−2atm (atmospheric pressure), and a Vanadium(V) oxide (V2O5) catalyst.

Two-step process for safely converting sulfur trioxide (SO3SO3​) into sulfuric acid (H2SO4H2​SO4​)

1. Dissolve SO3(g) in concentrated H2SO4(l) to form oleum: SO3(g)+H2SO4(l)→H2S2O7(l)

2. React oleum with water to form sulfuric acid.

H2​S2​O7​(l)+H2​O(l)→2H2​SO4​(l)

(Direct addition of SO3SO3​ to water is avoided because it produces a dangerous, uncontrollable acid mist).