“Equilibrium” What does it mean? What word does it look like? What does it mean? What word...

“Equilibrium”“Equilibrium”

What does it mean? What word does it look like?

What does it mean? What word does it look like?

Aim: How can we look at systems at equilibrium?

Aim: How can we look at systems at equilibrium?

Equilibrium: a state of balance

Dynamic Equilibrium: when overall rates of forward and reverse reactions are equal

This is a Reversible Equilibrium and is indicated by a double arrow

Equilibrium: a state of balance

Dynamic Equilibrium: when overall rates of forward and reverse reactions are equal

This is a Reversible Equilibrium and is indicated by a double arrow

Physical EquilibriumPhysical Equilibrium

Physical Equilibrium is balance in physical processes

Phase equilibrium: equilibrium between phases

Physical Equilibrium is balance in physical processes

Phase equilibrium: equilibrium between phases

Solution EquilibriumSolution Equilibrium

Solution Equilibrium: dissolving & crystallization happening at equal rate

Solution Equilibrium: dissolving & crystallization happening at equal rate

liquid-gasliquid-solid

Chemical EquilibriumChemical Equilibrium

CH4 (g) + H2O (g) 3 H2 (g) + CO (g) CH4 (g) + H2O (g) 3 H2 (g) + CO (g)

Chemical EquilibriumChemical Equilibrium

CH4 (g) + H2O (g) 3 H2 (g) + CO (g) CH4 (g) + H2O (g) 3 H2 (g) + CO (g)

HomeworkHomework

Finish equilibrium review pages Finish equilibrium review pages

Remember: Equilibrium is StabilityRemember: Equilibrium is Stability

CH4 + H2O 3 H2 + CO

Fwd rxn rate = Rev Rxn rate Using up reactants to make products

CH4 + H2O 3 H2 + CO

Fwd rxn rate = Rev Rxn rate Using up reactants to make products

How will a closed system react when a stress if applied?

How will a closed system react when a stress if applied?

equilibrium

stress

new equilibrium

Le Chatelier’s PrincipleLe Chatelier’s Principle

Closed systems will adjust to balance stresses Concentration, temperature, pressure

Shifts are increased reaction rates in either Fwd (right→) or Rev (left←) directions

Closed systems will adjust to balance stresses Concentration, temperature, pressure

Shifts are increased reaction rates in either Fwd (right→) or Rev (left←) directions

ConcentrationConcentration

Pen/pencil trick, pointing towards shift

A + B C

Add-Away, Take-Towards

Pen/pencil trick, pointing towards shift

A + B C

Add-Away, Take-Towards

https://www.youtube.com/watch?v=7zuUV455zFs

https://www.youtube.com/watch?v=7zuUV455zFs

ConcentrationConcentration Add-Away Add-Away

ConcentrationConcentration Take-Towards Take-Towards

Le Chatelier’s Principle:Temperature

Le Chatelier’s Principle:Temperature

Treat “heat/energy” like any other reactant

Adding heat favors reaction Removing heat favors reaction

Treat “heat/energy” like any other reactant

Adding heat favors reaction Removing heat favors reaction

N2 + 3 H2 2 NH3 + 22 kJN2 + 3 H2 2 NH3 + 22 kJ

12.6 kJ + H2 + I2 2 HI12.6 kJ + H2 + I2 2 HI

Do Now: Answer the following questionsDo Now: Answer the following questions

1. What is Le Chatelier’s Principle? 2. Label the forward and reverse reactions as

endothermic or exothermic:

CO (g) + 3 H2 CH4 (g) + H2O (g) + heat

3. In which direction will equilibrium shift if the temperature is increased?

4. In which direction will equilibrium shift if the temperature is decreased?

1. What is Le Chatelier’s Principle? 2. Label the forward and reverse reactions as

endothermic or exothermic:

CO (g) + 3 H2 CH4 (g) + H2O (g) + heat

3. In which direction will equilibrium shift if the temperature is increased?

4. In which direction will equilibrium shift if the temperature is decreased?

PressurePressure

Only for gases; count # of molecules on each side

If # is equal, pressure has no effect

pressure shifts towards fewer molecules

pressure shifts towards more molecules

Only for gases; count # of molecules on each side

If # is equal, pressure has no effect

pressure shifts towards fewer molecules

pressure shifts towards more molecules

Pressure ExamplePressure Example

4 NH (g) + 5 O2 (g) 4 NO (g) + 6 H2O (g)

= gas molecules = gas molecules

Increase pressure: shift (more to less) 9 10

Decrease pressure: shift (less to more) 9 10

4 NH (g) + 5 O2 (g) 4 NO (g) + 6 H2O (g)

= gas molecules = gas molecules

Increase pressure: shift (more to less) 9 10

Decrease pressure: shift (less to more) 9 10

N2 + 3 H2 2 NH3N2 + 3 H2 2 NH3

Equilibriumshift [N2] [H2] [NH3]

# molecules:

Increased pressure shifts towards fewer moleculesDecreased pressure shifts towards more molecules

H2 + I2 2 HIH2 + I2 2 HI

Equilibriumshift [H2] [I2] [HI]

# molecules:

Increased pressure shifts towards fewer moleculesDecreased pressure shifts towards more molecules

Conclusion QuestionsConclusion Questions

1. How does a system at equilibrium respond to a stress? List the factors that can be stresses on an equilibrium system.

1. How does a system at equilibrium respond to a stress? List the factors that can be stresses on an equilibrium system.

Conclusion QuestionsConclusion Questions

2. Given the reaction at equilibrium:

N2 (g) + 3 H2 (g) 2 NH2 (g) + heat

Which stress would cause the equilibrium to shift to the left? (a) Increasing the temperature (b) Adding N2 (g) to the system (c) Adding H2 (g) to the system

2. Given the reaction at equilibrium:

N2 (g) + 3 H2 (g) 2 NH2 (g) + heat

Which stress would cause the equilibrium to shift to the left? (a) Increasing the temperature (b) Adding N2 (g) to the system (c) Adding H2 (g) to the system

Conclusion QuestionsConclusion Questions

2. Given the reaction at equilibrium:

N2 (g) + O2 (g) 2 NO (g)

If the concentration of N2 (g) is increased, the concentration of O2 (g) will (a) Decrease (b) Remain the same (c) Increase

2. Given the reaction at equilibrium:

N2 (g) + O2 (g) 2 NO (g)

If the concentration of N2 (g) is increased, the concentration of O2 (g) will (a) Decrease (b) Remain the same (c) Increase