Introduction to Equilibrium Chemistry

Le Chatlier's Principle

Amadi, C

Open Ended

When you hear this principle, what is the first thing that comes to mind? Don't google it! 😂

Le Chatelier's States...

when a chemical system is at equilibrium and is disturbed by a stress, the system will respond by attempting to counteract that stress until a new equilibrium is established.

What factors affect the chemical equilibrium?

Concentration

Temperature

Pressure

Concentration

If the concentration of one substance in a system is increased, the system will respond by favoring the reaction that consumes that substance.

Temperature

Endothermic and Exothermic

Pressure

A change in the pressure on a liquid or a solid has a negligible effect.

 Imagine the gases are contained in a closed system in which the volume of the system is controlled by an adjustable piston 

Multiple Choice

What happens to the equilibrium if we add methane (CH₄)?

• It shifts left, towards the reactants

• It shifts right, towards the products

• It does not shift

Multiple Choice

What happens to the equilibrium if we remove heat?

• It shifts left, towards the reactants

• It shifts right, towards the products

• It does not shift

Multiple Choice

What happens to the equilibrium if we remove water (H₂O)?

• It shifts left, towards the reactants

• It shifts right, towards the products

• It does not shift

Multiple Choice

The three factors that affect the equilibrium of a reaction are temperature, pressure and __________. 

• energy
• concentration 
• enthalpy 
• ice 

Multiple Choice

For the reaction...
N_{2 (g)} +  3 H_2 (g) <−> 2 NH_{3 (g)}

If the pressure in the system is increased, the reaction will __________________.

•  shift to the left
• shift to the right
• not shift

Multiple Choice

For the reaction...
SO_2(g) + O_2(g) <−>  SO_3(g)
If the concentration of SO_2(g)  is increased, the equilibrium of the reaction will ___________.

• shift to the left
• shift to the right
• not shift

Multiple Choice

An exothermic reaction is allowed to reach equilibrium. If heat energy is then removed, the equilibrium will shift

• toward the middle
• toward the reactant side
• toward the product side

Multiple Choice

When writing an endothermic reaction, heat energy is stated as

• product
• catalyst
• reactant

Multiple Choice

Le Chaltelier's Principle states that if a chemical system at equilibrium is stressed,

• the system will adjust to increase the stress
• the system will adjust to reduce the stress
• the system will not adjust

3 Questions After the Video

​Fe³⁺ + SCN <--> FeSCN²⁺

1. Increasing the SCN^- concentration shifted the reaction to the right or left?

2. Increasing the Fe³⁺ concentration shifted the reaction ot the right or left?

3. Decreasing the Fe³⁺ concentration (by adding Na₂HPO₄ shifted the reaction right or left?

Open Ended

1. Increasing the SCN^- concentration shifted the reaction to the right or left? What's your evidence?

Fe⁺³ (aq) + SCN^- (aq) « FeSCN⁺² (aq)

Open Ended

1. Increasing the Fe⁺³ concentration shifted the reaction to the to the right or left? What's your evidence?

Fe⁺³ (aq) + SCN^- (aq) « FeSCN⁺² (aq)

Open Ended

1. Decreasing the Fe⁺³ concentration (by adding Na₂HPO₄) shifted the reaction to the right or left? What's your evidence?

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq)

Multiple Choice

Because the reaction Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) is exothermic, which formula would you use?

• Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

• Fe⁺³ (aq) + SCN^- (aq) + Heat <--> FeSCN⁺² (aq)

• Fe⁺³ (aq) + SCN^- (aq) + Heat <--> FeSCN⁺² (aq) + Heat

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Increasing the temperature of this reaction would shift the equilibrium...

• Towards the products, forward reaction

• Towards the reactants, reverse reaction

• It wouldn't affect equilibrium

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Because the reactants are yellow, and the products are red. What would the test tube look like after DECREASING the temperature?

• Yellow

• Red

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Because the reactants are yellow, and the products are red. What would the test tube look like after INCREASING the temperature?

• Yellow

• Red

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Because the reactants are yellow, and the products are red. What would the test tube look like after increasing the concentration of FeSCN?

• Yellow

• Red

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Because the reactants are yellow, and the products are red. What would the test tube look like after increasing the concentration of Fe⁺³?

• Yellow

• Red

Multiple Choice

1. Decreasing the pressure of the reaction will shift the equilibrium...

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq)

• Right towards the products

• Left towards the reactants

• It won't affect equilibrium

Multiple Choice

Fe⁺³ (aq) + SCN^- (aq) <--> FeSCN⁺² (aq) + Heat

Because the reactants are yellow, and the products are red. What would the test tube look like after Decreasing the concentration of SCN^-?

• Yellow

• Red