Equilibrium Basics

Question 1

Equilibrium

Chemical Equilibrium

Answer 1

Occurs when opposing rxn proceeds at equal rates
* Concentrations dont change with time making rxn appear stopped

Question 2

Equilibrium

What is K?

Answer 2

• Equilibrium Constant
• = [A]eq/[B]eq = Pressure of A eq/ Pressure of B eq
• At Constant Temperature
• K&raquo_space;1(>10): Equilibrium favors product formation
• K «1( <.10): Equilibrium favors reactant formation

Question 3

Equilibrium

Law of Mass Action for general rxn

Answer 3

• Kc = [C]^c * [D]^d/([A]^a * [B]^b)
• Kp same just with P instead of [ ]

Question 4

Equilibrium

Rules

Answer 4

• Solids not considered
• Liquid water when in excess not considered

Question 5

Equilbrium

Converting from Kc–>Kp

Answer 5

• Kp=Kc(RT)^∆n
• R = .08206

Question 6

Modifying Equilibrium Expressions

Types of Modification

Answer 6

1. Reversing Equation: K’c = 1/Kc
2. Multiplying Equation by x: K’c = Kc^x
3. Adding 2 equations: K’c = Kc1 * Kc2

Question 7

Rxn Quotient

What is it?

Answer 7

• Qc/ Qp
• Concentration ratio for Kc/Kp at non equilibrium conditions
• Not constant but allows us to predict direection of net change

Question 8

Rxn Quotient

How it helps us predict

Answer 8

• Q > K ==> backward rxn favored
• Q < K ==> forward rxn favored

Question 9

ICE Table

What are they?

Answer 9

1. I: Initial [ ] or P
2. C: Change over time
3. E: When at Equilibrium

Question 10

Le Chat’s principle

What is it?

Answer 10

• Predicts how eq’m restored
• System will react to stress

Question 11

Le Chat’s Principle

Adding or Removing a Substance in rxn

Answer 11

• Adding: system will shift and increased rate of rxn that decreases [substance]
• Removing: system will shift and decrease rate of rxn that decreases [substance]

Question 12

Le Chat’s Principle

Stress sys by changing T

Answer 12

• Exo:
  
  1. Increased T = Increased R and Decreased P
  2. Decreased T = Increased P and Decreased R
• Endo:
  
  1. Increased T = Increased P and Decreased R
  2. Decreased T = Increased R and Decreased P

Question 13

Le Chat’s Principle

Change P or V of Sys

Answer 13

• As P increases or V decreases(decrease space)
  
  • eq net shift to side with less number of moles of gas
• As P decreases or V increases(increase space)
  
  • Shift to side with more moles of gas
• If number of moles reactant = number of moles product, then there is no shift

Question 14

Le Chat’s Priniciple

Special Cases

Answer 14

1. Partial Pressures of reacting changes does change with adding or removing inert gases
2. In a rigid container: Total Pressure will increase but Partial Pressures don’t(no shift)
3. Constant External Pressure[balloon/ moveable piston]
   
   4. Same as ∆Pressure

Question 15

Le Chat’s Principle

Changes that will not cause Eq. Shift

Answer 15

1. Adding Inert Gas to constant volume container
2. Catalyst
3. Pure solids or Liquids