Concentration

Concentration:

• A change in concentration by the addition or removal of a reactant or product will cause a shift in the equilibrium.
• Concentration changes by adding or removing an atom or molecule (change in moles)

What if the concentration changes:

• REMOVING REACTANT OR PRODUCT:
• Equilibrium shifts in the direction that will replace the reactant or product that was removed.
• ADDING REACTANT OR PRODUCT:
• Equilibrium shifts in the direction that will use up the reactant or product that was added.

Examples:

• 
• 
• Bildunterschrift: THE DECREASE OF THE REACTANT A CAUSES THE EQUILIBRIUM TO MOVE TO THE LEFT AS IT NEEDS PRODUCTS TO FILL ITS PLACE. (PRODUCTS WILL DECREASE)
• Bildunterschrift: THE INCREASE OF REACTANT A CAUSES THE EQUILIBRIUM TO MOVE TO THE RIGHT IN ORDER TO MAKE USE OF IT AND MAKE PRODUCTS. (PRODUCTS WILL INCREASE)

EXAMPLE QUESTION 1:

• The reaction shown in the equation below is at equilibrium.
• CO(g) + 2H2(g) CH3OH (g)
• Describe the effect of each of the following changes on the equilibrium concentration of
• methanol (increase, decrease, stay the same).
• Justify your answers using equilibrium principles.
• H2(g ) is removed.
• Amount of CH3OH(g) would: increase OR decrease OR stay the same
• (circle correct answer)

Example Question 1 answer:

• 
• MAIN POINTS:
• - Equilibrium will shift to the left.
• - CH30H will be used to replace H2
• - Therefore the amount will decrease.