Le Chatelier's Principles

Question 1

Le Chatelier’s Principle

Answer 1

When a stress is applied to a system at equilibrium, the system will shift in a way to minimize this stress and reestablish equilibrium

Question 2

What are the 4 stressors/factors that affect chemical reactions?

Answer 2

1) Addition/Removal of a substance
2) Changes in pressure or volume
3) Changes in temperature
4) Presence of Catalyst

Question 3

If products are removed OR reactants are added:

Answer 3

RXN proceeds FWD
*Q becomes smaller than Kc

Question 4

If reactants are removed OR products are added:

Answer 4

RXN proceeds REV
*Q becomes larger than Kc

Question 5

If Pressure increases

Answer 5

Then volume decreases. RXN will shift to whichever direction has less moles of gas.
*To determine which direction has less moles of gas look at coefficient of molecules in gas state and add together

Question 6

If volume decreases

Answer 6

Then pressure increases. RXN will shift to whichever direction has less moles of gas.
*To determine which direction has less moles of gas look at coefficient of molecules in gas state and add together

Question 7

If pressure decreases

Answer 7

Then volume increases. RXN will shift to whichever direction has MORE moles of gas.
*To determine which direction has more moles of gas look at coefficient of molecules in gas state and add together

Question 8

If volume increases

Answer 8

Then pressure decreases. RXN will shift to whichever direction has MORE moles of gas.
*To determine which direction has more moles of gas look at coefficient of molecules in gas state and add together

Question 9

For PV = nRT, if n and T are constant in a reaction at equilibrium then….

Answer 9

P is proportional to 1/V

Question 10

An Exothermic reaction equation

Answer 10

[reactants]<–> [products] + Δ

Question 11

An Endothermic reaction equation

Answer 11

Δ + [reactants] <–> [products]

Question 12

If temperature increases in an exothermic reaction

Answer 12

RXN proceeds in REV

Question 13

If temperature increases in an endothermic reaction

Answer 13

RXN proceeds in FWD

Question 14

If temperature decreases in an exothermic reaction

Answer 14

RXN proceeds in FWD

Question 15

If temperature decreases in an endothermic reaction

Answer 15

RXN proceeds in REV

Question 16

When a catalyst is present then…

Answer 16

The RXN does not shift and remains at equilibrium.
Catalyst lowers the activation energy of both the forward and reverse rates, so the Rate forward is equal to the Rate reverse.