For the reaction N₂(g) + 3H₂(g)  2NH₃(g) ΔH = -ve : 

Concept:

Haber's process:

• This process is used in large scale preparations of ammonia.

N2 + 3H2 → 2NH3

• During the process, nitrogen and hydrogen are used in the ratio 1:3.
• The process is exothermic ΔH = -ve  in nature means heat is produced in the process.
• According to the Le-chateliar principle, the temperature is kept high to speed up the process.
• The gaseous ammonia produced is converted to liquid ammonia to remove the products formed.
• This drives the reaction forward.

Equilibrium Constants:

• ​The constants K_p and K_c are both equilibrium constants.
• K_p is used when the concentration terms are given in partial pressures i.e, in gaseous reactions.
• K_c is used when the reaction terms are expressed in molarities.
• The relation between K_p and K_c is given by:

 where R = Universal gas constant, T = Temperature, and  = change in moles of gases in the reaction.

Calculation:

• ​The relation between K_p and K_c is

For the reaction

N2(g) + 3H2(g)  2NH3(g)

Hence,

Hence, or the reaction N2(g) + 3H2(g)  2NH3(g) ΔH = -ve,