La chatalier's principle and Pressure.

https://www.youtube.com/watch?v=W1HDDeX4cPM

What is key idea about gas pressure

Gas pressure is proportional to the number of moles of gas present.

What happens if we increase pressure

Causes equilibrium to shift towards the side with fewer moles of gas to oppose the change, and thereby reduce the pressure

What happens if we decrease pressure

Decreasing pressure will cause the equilibrium to shift towards the side with more moles of gas to oppose the change, and thereby increase the pressure

What effect would increaasing pressure have on the yield of methanol

If pressure is increased the equilibrium will shift to oppose this and move towards the side with fewer moles of gas to try to reduce the pressure. The position of equilibrium will shift towards the right because there are 3 moles of gas on the left but only 1 mole of gas on the right, giving a higher yield of methanol.