Le Châtelier’s Principle

If stress is applied to a system the system shifts to relieve the stress

Le Châtelier’s Principle

Mountains and mole-hills:

If stress is added the reaction must shift in the opposite direction to “remove” the mountain

If stress is removed the hole must shift in the same direction to “fill in” the hole

Change in Concentration

Which direction will the reaction

shift if the concentration of CO is increased?

Change in Concentration

To even out the pile it must shift right

Which direction will the reaction

shift if the concentration of CO is decreased?

Change in Concentration

To even out the pile it must shift left

Which direction will the reaction

shift if the concentration of CH4is increased?

Change in Concentration

SHIFT LEFT

Which direction will the reaction

shift if the concentration of H2 is decreased?

Change in Concentration

SHIFT LEFT

Which direction will the reaction

shift if the concentration of H2O is decreased?

Change in Concentration

SHIFT RIGHT

Which direction will the reaction

shift if the concentration of H2 is increased?

Change in Concentration

SHIFT RIGHT

Remember that decreasing volume

is also increasing pressure If pressure is increased, the

reaction shifts to the side with the least amount of moles

Changes in Volume

What will happen if volume is

decreased?

Changes in Volume

Changes in VolumeThe reaction

shifts towards the right to

relieve stress

Which direction will the reaction

shift if the volume is decreased?

Changes in Volume

There would be no change because there are equal moles

on each side!!!

Temperature changes like

concentration…mountains and mole-hills

Changes in Temperature

Which direction will the reaction

shift if heat is added? What will happen if heat is

removed?

Changes in Temperature

Changes in Temperature

If heat is on the right side of the

reaction, it is exothermic If heat is on the left side of the

reaction, it is endothermic

Just a Note…

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