Chapter 17. Equilibrium: The Extent of Chemical Reactions
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17.1The Equilibrium State and the Equilibrium Constant
17.2The Reaction Quotient and the Equilibrium Constant
o The Changing Value of the Reaction Quotient
o Writing the Reaction Quotient (Q)
17.3Expressing Equilibria with Pressure Terms: Relation between Kc and Kp
17.4Comparing Q and K to Determine Reaction Direction
17.5How to Solve Equilibrium Problems
o Using Quantities to Find K
o Using K to Find Quantities
o Problems Involving Mixtures of Reactants and Products
17.6Reaction Conditions and Equilibrium: Le Châtelier's Principle
o Change in Concentration
o Change in Pressure (Volume)
o Change in Temperature
o Lack of Effect of a Catalyst
o Synthesis of Ammonia
Concepts and Skills to Review Before You Study This Chapter
1.
reversibility of reactions (Section 4.7)
2.
equilibrium vapor pressure (Section 12.2)
3.
equilibrium nature of a saturated solution (Section 13.4)
4.
dependence of rate on concentration (Sections 16.2 and 16.5)
5.
rate laws for elementary reactions (Section 16.6)
6.
function of a catalyst (Section 16.7)
n(gas)
Kp = Kc (RT)
1) N2(g) + 3 H2(g)  2 NH3(g) + heat
1. Stress : increase [NH3]
N2(g) + 3 H2(g)  2 NH3(g) + heat
2. Stress : increase temp
N2(g) + 3 H2(g)  2 NH3(g) + heat
Note : delta T will change K value
3. Stress : decrease the volume
4. Stress : add inert gas
N2(g) + 3 H2(g)  2 NH3(g) + heat
N2(g) + 3 H2(g)  2 NH3(g) + heat
2) 2 SO2(g) + O2(g)
2 SO3(g) Given the equilibrium concentrations of SO3: 0.120M
0.860M
O2: 0.330M, calculate the value of Kc for this reaction.
SO2:
3) For the reaction system, 2 SO2(g) + O2(g)
2 SO3(g), Kc has a value of 4.62 at 450.0 K. A
system, at equilibrium has the following concentrations: [SO3] = 0.254 M, [O2] = 0.00855 M. What is
the equilibrium concentration of SO2?
4) The equilibrium constant for the reaction, H2(g) + I2(g)
2 HI(g) is 54.9 at 699.0 K. What is
the equilibrium constant for 4 HI(g)
2 H2(g) + 2 I2(g) under the same conditions?
2 NO(g) + Cl2(g)
2 NOCl(g)
Kc = 3.20 x 10-3
2 NO2(g)
2 NO(g) + O2(g)
Kc = 15.5
calculate a value for Kc for NOCl(g) + ½ O2(g)
NO2(g) + ½ Cl2(g).
5) Using this data,
6) H2(g) + I2(g) <--> 2HI(g) 0.00500mol of H2 and 0.0100mol of I2 is placed in a 5.00L container at
448C. At eq.,[HI] = 0.00187M. Setup ICE table to calculate K.
7) A study of the system, 4 NH3(g) + 7 O2(g)
2 N2O4(g) + 6 H2O(g), was carried out. A
system was prepared with [NH3] = [O2] = 3.60 M as the only components initially. At equilibrium,
[N2O4] is 0.60 M. Calculate the equilibrium concentration of O2.
8) Predict the direction of the reaction?
N2(g) + 3 H2(g) <--> 2 NH3(g)
K = 0.060 L^2 / mol^2 at 500.C
initial [NH3] = 0.0010M initial [N2] = 0.000010M initial [H2] = 0.0020M
9) At 25°C, the equilibrium constant Kc for the reaction, 2A(g)
B(g) + C(g), is 0.035. A mixture of
8.00 moles of B and 12.00 moles of C in a 20.0 L container is allowed to come to equilibrium. What is
the equilibrium concentration of A?
10) What are [ ]eq of each ?
CO(g) + H2O(g) <--> CO2(g) + H2(g)
[ ]initial = 1.00M for all 4 species
Kc = 5.10 at 700.K
11) If 2.00M HF dissociates 1.3% in water, what is the K for HF(aq) + H2O(l)  H3O+ (aq) + F- (aq)?