le chateliers principle

Question 1

define: position of equilibrium

Answer 1

the relative amounts of reactants and products at equilibrium.

Question 2

what can POE be changed by

Answer 2

• Adding/removing a reactant/product
• Changing pressure by changing volume (gases)
• Dilution (solution)
• Changing temperature

Question 3

why doesn’t POE equal Kc

Answer 3

bc affected by other factors in addition to temperature.

Question 4

define: le chateliers principle

Answer 4

if an equilibrium system is subjected to a change, the system will adjust itself to partially oppose the effect of the change.

Question 5

important points for concentration time graphs?

Answer 5

• Points on time axis
o Where the change occurs
o Where the new equilibrium is established (all concentrations are constant)
• At new equilibrium, the concentrations are different from the original concentrations.
• Take mole ratio into account: the bigger the number, the bigger the change in concentration

Question 6

what happens when you add extra reactant? (also need to know for extra product)

Answer 6

conc of reactant instantaneously increases. The system will partially oppose this change by increacing conc of product, resulting in a net forwards reaction.

Question 7

what happens when you reduce the volume to increase the pressure

Answer 7

System will partially oppose the increase in pressure by decreasing the pressure – causing a net reaction in the direction in which there are less product particles than reactant particles

Question 8

what happens when you increase the pressure by adding an inert gas?

Answer 8

It doesn’t affect the conc of reactants and products, and hence position of equilibrium

Question 9

what happens when they’re diluted?

Answer 9

This reduces the number of particles per volume; the system will partially oppose this change by causing net reaction in which there are more product particles than reactants.

Question 10

what happens when you increase the temperature?

Answer 10

The average kinetic energy of substances in the mixture increases. This change is partially opposed by absorbing energy.
For endothermic reactions: net forward reaction
For exothermic reactions: net backwards reaction

Question 11

what happens when you add a catalyst?

Answer 11

(explain)… increases the rate of both forwards and backwards reactions equally. However this doesn’t alter the position of equilibrium. Stays the same.

Question 12

factors increasing the yield of a chemical reaction?

Answer 12

• Temperature: low for exothermic, high for endothermic
• Pressure: depends on relative numbers of reactants and products
• Adding extra reactant
• Removing product as it forms.