Learning Goals

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Learning Goals
• identify common equilibrium constants,
including Keq, Ksp, Kw, Ka, Kb and write the
expressions for each
• solve problems related to equilibrium by
performing calculations involving
concentrations of reactants and products
Equilibrium Law
• mathematical description of chemical system
at equilibrium
• defined by the equilibrium constant, K
• Complete Inv. 7.2.1 on p. 473-474
Writing Equilibrium Law Equations
For aA + bB
cC + dD,
K = [C]c[D]d
[A]a[B]b
(omit units)
• omit (s) and (l)
• include only (aq) and (g)
Ex. H2(g) + S(l)
H2S(g)
Ex. NH3(g) + H2O(l)
NH4+(aq) + OH-(aq)
p. 431 #1-3, p. 434 #1
Calculating K
• Write the equilibrium law equation.
• Substitute [ ]eq
• K can be used to predict the equilibrium
position (Review Equilibrium Position table in
lesson 1 and add a column for K.)
• Sample Problem 2 (p. 430)
In a closed vessel at 500°C, N2(g) + 3 H2(g)
2 NH3(g)
The equil. conc. of N2, H2 and NH3, respectively, are
1.50 x 10-5 M, 3.45 x 10-1 M and 2.00 x 10-4 M.
Calculate K.
• Sample Problem 3 (p. 431)
In a closed vessel at 500°C, 2 NH3(g)
H2(g)
N2(g) + 3
The equil. conc. of N2, H2 and NH3, respectively, are
1.50 x 10-5 M, 3.45 x 10-1 M and 2.00 x 10-4 M.
Calculate K.
K (synthesis of ammonia)
K’ (decomposition of ammonia)
Mathematical relationship b/w K and K’?
K = 1/K’
What does the magnitude of K tell us
about the equilibrium position?
A. In a closed system at 25°C,
2 CO(g) + O2(g)
2 CO2(g) K = 3.3 x 1091
B. Decomposition of water at 1000°C,
2 H2O(g) 2 H2(g) + O2(g) K = 7.3 x 10-10
C.
NO2(g) + NO(g)
N2O(g) + O2(g) K = 0.951
Homework
• p. 436 #1-6
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