o “K” :

Manipulation of K

Kp verse Kc

C16: EQUILIBRIUM Write an equilibrium constant expression for any

chemical reaction. The concentrations of solids and solvents (e.g., water) are not included in equilibrium constant expressions

Recognize that a large value of K (K>> 1) means the reaction is product-favored. A small value of K (K << 1) indicates a reactant-favored reaction.

Use equilibrium constants to calculate the concentration of a reactant or product at equilibrium.

Apply Le Chatelier’s principle to predict the effect of a disturbance on a chemical equilibrium: a change in temperature, a change in concentrations, or a change in volume or pressure for a reaction involving gases

• Calculate an equilibrium constant given the reactant and product concentrations at equilibrium

• Apply the idea of the reaction quotient (Q) to decide if a reaction is at equilibrium.Q = K; reaction is at equilibriumQ <K ;net conversion of reactants to products Q >K; products convert to reactants to attain equilibrium

TODAY: KP

K is designated as Kc when

Equilibrium concentrations are expressed in terms of reactant and product

concentration, M (moles per liter).

K is designated as Kp, when concentrations of gases are

represented by partial pressures (amount of gas measured in atm

or Kpa)

TODAY: K MANIPULATION

Know how K changes as different stoichiometric coefficients are used in a balanced equation and when equation is reversed

Know that, when two chemical equations are added to give a net equation, the value of K for the net equation is the product of the values of K for the summed equations

WHAT IF THE EXPRESSION ONLY CONTAINS GASES?

Kp

2NO2 + O2

↔ 2NO3

2H2O + CH4 a CO2

+4H2H2 + I2 ↔ 2HI

KP =

S(s) + O2(g) ---> SO2(g)

Fe3+(aq) + SCN-(aq) a FeSCN2+

3H2(g) + N2(g) a 2NH3(g)

Kp verse Kc

MANIPULATING “K”

K3 = K1* K2

K3 = K1

K2

Kw = Ka* Kb