The reaction for the Haber process is shown below. N2(g) + 3H2(g) ⇌ 2NH3(g) What will be the effect of increasing the pressure on the amount of ammonia present at equilibrium? [1 mark]
Increase.
This question is looking at a reversible reaction - the reaction can occur both forwards and backwards.
Firstly to answer this question you need to appreciate that in a closed reaction the equilibrium (the balance of the rate of forward/backward reaction) will shift to favour the side which opposes a change to the environment. So if you increase the external pressure --> the equilibrium will shift to favour the reaction that decreases the pressure. So what decreases the pressure? A lesser number of moles being produced, as more moles = more pressure in a given volume. Now you need to look at which reaction produces the least amount of moles. You do this by counting up the number of moles on each side:
N2+ 3H2 = 1 + 3 =42NH3= 2
As you can see the forward reaction produces the least number of moles (4 --> 2 ) and also produces ammonia. Therefore more ammonia would be produced if the pressure was increased.
