Chapter 15: Chemical Equilibrium

Question 1

Reaction quotient

Answer 1

Q_c

Fraction written with
product concentrations in numerator, and
reactant concentrations in the denominator

*with each concentration raised to a power equal to the corresponding stoichiometic coefficient

*always has same value when at constant pressure, regardless of initial concentrations

aA + bB = cC + dD

Q_c = [C]^c[D]^d / [A]^a[B]^b
(Subscript c = concentration)

Question 2

Equilibrium constant

Answer 2

K_c

For a system at equilibrium, K_c (equil. constant) = Q_c (reaction quotient)

Question 3

Law of mass action

Answer 3

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

Question 4

Equilibrium expression

Answer 4

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

Equilibrium expression is the:
equilibrium constant = (reaction quotient)

Question 5

Equilibrium chart (chart of death)

Answer 5

Columns:

• Initial Concentration
• Change (delta)
• Equilibrium Concentration

Rows:
Reactants & products

Question 6

La Châtelier’s principle

Answer 6

When a stress is applied to a system at equilibrium, the system will respond by shifting in the direction that minimizes the effect of the stress

Question 7

Reversible process

Answer 7

A process in which the products can react to form reactants

Question 8

Equilibrium

Answer 8

A state in which forward and reverse processes are occurring at the same rate

Question 9

Equilibrium constant for gases

Answer 9

K_p

P = pressure

K_c does not equal K_p because the partial pressures of reactants and products expressed in atmospheres are not equal to their concentrations (mol/L or M)

K_p = (P_B)^b / (P_A)^a –> K_p = K_c(RT)^Δn
where Δn = b - a
(moles of gaseous products - moles of gaseous reactants)

(P_B and P_A are partial pressures)