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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