Equilibrium

Question 1

Dynamic Equilibrium

Answer 1

The point at which the rate of the forwards reactions EQUALS the rate of the reverse reaction

–> Rates are equal = Concs. are CONSTANT

–> Concentrations do not have to be equal

Question 2

Equilibrium Constant

Answer 2

K: “Big k”

–> Defines the conditions at equilibrium

K = Ratio at EQUILIB of the product of conc. of products raised to their coeffs. divided by the product of conc. of reactants raised to their coeffs

K = [C]^c [D]^d / [A]^a [B]^b

Question 3

Law of Mass Action

Answer 3

The law that tells us K is equal to that specific ratio

Question 4

K > 1

Answer 4

Equilibrium lies “to the right”

–> The forwards rxn. was favored to get to equilibrium

–> There are > products than reactants at equilibrium

Question 5

K < 1

Answer 5

Equilibrium lies “to the left”

–> The reverse rxn. was favored to get to equilibrium

–> There are > reactants than products at equilibrium

Question 6

K = 1

Answer 6

Equilibrium does not lie to either side

–> No rxn . direction was favored to reach equilibrium

–> Products ~ Reactants at equilibrium

Question 7

ICE Tables

Answer 7

A method for finding the concs. at equilibrium from initial concs.

I = Initial concs.
C = Change in conc. (in terms of x)
E = Equilibrium concs.

*C is dependent upon stoichiometric coeffs AND reactant (-) vs product (+)

Question 8

Effect on K of Reversing Rxn.

Answer 8

K(reverse) = 1 / K(forwards)

–> Take the inverse (flip K value around) when equation is reversed

Question 9

Effect on K of Multiplying Coeffs. by a Factor

Answer 9

If coefficients are multiplied by a factor (n), raise K to the power of n

K(new) = (K original)^n

Question 10

Effect on K of Adding Two or More Equations Together

Answer 10

If 2 or more equations are added together to get an overall equation, multiply their individual K values to get K overall

K(overall) = K1 * K2 * etc…

Question 11

Converting Between Kp and Kc

Answer 11

Kp = Kc(RT)^delta n

R = 0.08206
T = temp in K
delta n = Change in moles
= (Sum of product coeffs.) - (Sum of reactant coeffs.)

Question 12

Reactions with Solids and Liquids

Answer 12

Pure solids and liquids are NOT INCLUDED in K value

–> Due to their concentration being constant

Question 13

Reaction Quotient

Answer 13

Q = Measure of the progress of a rxn. towards equilibrium

Q = same ratio as K BUT with concs. at any point in rxn. (doesn’t have to be at equilib)

–>Tells us how to get to equilibrium/how far we are from it

Question 14

Q > K

Answer 14

Reaction will move LEFT

–> Reverse rxn. is favored

–> Rxn. currently has > products and < reactants

Question 15

Q < K

Answer 15

Reaction will move RIGHT

–> Forwards rxn. is favored

–>Rxn. currently has < products and > reactants

Question 16

Q = K

Answer 16

Rxn. is AT equilibrium

–> No rxn. direction is favored

Question 17

“x is small” Approximation

Answer 17

If K has an exponent multiplier (10^n) that is equal to or more negative than -5 (<= -5), it is safe to remove x (usually from denominator) and approximate

Question 18

Le Chatlier’s Principle

Answer 18

When a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes that disturbance

–> A system at equilibrium wants to stay at equilibrium (will do what it can to “bounce back” when disrupted)

Question 19

Equilibrium Disturbance:

Increase in reactant conc.

Answer 19

= Shift to the RIGHT (forwards rxn.)

(Q < K)

Question 20

Equilibrium Disturbance:

Decrease in product conc.

Answer 20

= Shift to the RIGHT (forwards rxn.)

(Q < K)

Question 21

Equilibrium Disturbance:

Increase in product conc.

Answer 21

= Shift to the LEFT (reverse rxn.)

(Q > K)

Question 22

Equilibrium Disturbance:

Decrease in reactant conc.

Answer 22

= Shift to the LEFT (reverse rxn.)

(Q < K)

Question 23

Equilibrium Disturbance:

Increase in Volume /
Decrease in Pressure

Answer 23

= Rxn. shifts in direction with MORE # moles of GAS

Question 24

Equilibrium Disturbance:

Decrease in Volume /
Increase in Pressure

Answer 24

= Rxn. shifts in direction with LESS # moles of GAS

Question 25

Equilibrium Disturbance:

Changing Temps of EXO-Thermic Rxn.

Answer 25

Heat is treated as a product

–> Increase temp = Shift LEFT
–> Decrease temp = Shift RIGHT

Question 26

Equilibrium Disturbance:

Changing Temps of ENDO-Thermic Rxn.

Answer 26

Heat is treated as a reactant

–> Increase temp = Shift RIGHT
–> Decrease temp = Shift LEFT

Question 27

When does Kp = Kc?

Answer 27

When delta n = 0