Huber process

1

Explain Haber process

Reply 1

10

Ok so hydrogen and nitrogen are cycled into a container/tank and (under certain conditions such as the PRESENCE OF A CATALYST) form Nh3, which is needed for fertilisers. The unreacted hydrogen and nitrogen are recycled back into the tank until all products are used up. For 6 markers, know about the special conditions that favour the reactions as this reactions is a REVERSIBLE one. Soz if I explained this badly :smile:

Reply 2

TypicalNerd

18

Original post

by ZarFo

Ok so hydrogen and nitrogen are cycled into a container/tank and (under certain conditions such as the PRESENCE OF A CATALYST) form Nh3, which is needed for fertilisers. The unreacted hydrogen and nitrogen are recycled back into the tank until all products are used up. For 6 markers, know about the special conditions that favour the reactions as this reactions is a REVERSIBLE one. Soz if I explained this badly :smile:

To add onto your reply, the reaction is carried out using an iron-based catalyst with the reaction heated to 450 C under a pressure of 200 atm.

The iron-based catalyst does not have an effect on the position of the equilibrium, but it does accelerate the forward and backward reaction routes equally meaning equilibrium is reached faster. This is because catalysts offer alternative reaction pathways with lower activation energies for both the forward and backwards reactions.

The reaction is exothermic, so the high temperature isn't favourable to the yield (which at equilibrium is only around 15% iirc), but it does cause the reaction to proceed much more rapidly as the molecules have more kinetic energy on average and therefore it is more likely that particles will collide with sufficient energy so you get more frequent, successful collisions per second (e.g a faster rate of reaction). This is a compromise condition.

The high pressure is to maximise the yield, since there are fewer moles of gas on the products side than the reactants (N2 (g) + 3H2 (g) --> 2NH3 (g) - 4 mol on the LHS vs 2 mol on the RHS). You also speed up the reaction because the molecules are forced closer together and so are more likely to collide.

Another thing to consider is that the ammonia is removed as it is produced (the way they do this is beyond GCSE, but they use the fact ammonia liquefies at a higher temperature than H2 and N2 to separate it out before sending the nitrogen and hydrogen back into the reactor). This disrupts the equilibrium and pushes it to the right to replace the ammonia taken out. Recycling leftover N2 and H2 removed also helps to push the equilibrium to the right.

Huber process

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