OHS AP Chemistry – Chapter 16 Quiz

OHS AP Chemistry – Chapter 16 Quiz
1. Decide if each of the following statements is true or false. If false, change the wording to
make it true.
The magnitude of the equilibrium constant is always independent of temperature.
When two chemical equations are added to give a net equation, the equilibrium
constant for the net equation is the product of the equilibrium constants of two equations.
The equilibrium constant for a reaction has the same value as K for its reverse.
Only the concentration of CO2 appears in the equilibrium constant expression for
the reaction CaCO3(s) ↔ CaO(s) + CO2(g).
For the reaction CaCO3(s) ↔ CaO(s) + CO2(g), the value of K is numerically the
same whether the amount of CO2 is expressed as moles per liter or as gas pressure.
2. If the reaction quotient (Q) is smaller than the equilibrium constant(K)for a reaction such as
A ↔ B, does this mean that reactant A continues to be consumed to form B, or does B form A,
as the system moves to equilibrium? Explain the reason for your answer.
3. Write equilibrium constant expressions for the following reactions. For gases use either
pressure or concentrations.
(a) 3 O2(g) ↔ 2 O3(g)
(b) Fe(s) + 5 CO(g) ↔ Fe(CO)5(g)
(c) (NH4)2CO3(s) ↔ 2 NH3(g) + CO2(g) + H2O(g)
(d) Ag2SO4(s) ↔ 2 Ag+(aq) + SO42−(aq)
4. An equilibrium mixture of SO2, O2, and SO3 at 1000 K contains the gases at the following
concentrations: [SO2] = 3.77 × 10−3 mol/L. [O2] = 4.30 × 10−3 mol/L, and [SO3] = 4.13 × 10−3
mol/L. Calculate the equilibrium constant, Kc, for the reaction
2 SO2(g) + O2(g) ↔ 2 SO3(g)
5. A mixture of SO2, O2 and SO3 at 1000 K contains the gases at the following concentrations:
[SO2] = 5.0 × 10−3 mol/L, [O2] = 1.9 × 10−3 mol/L, and [SO3] = 6.9 × 10−3 mol/L. Using the
Kc calculated in question 4, determine if this reaction is at equilibrium. If not, which way will
the reaction proceed to reach equilibrium?
2 SO2(g) + O2(g) ↔ 2 SO3(g)
6. The equilibrium constant for the reaction N2O4(g) ↔ 2 NO2(g)
at 25°C is 5.88 × 10−3. Suppose 0.156 g of N2O4 is placed in a 5.00-L flask at 25°C.
2 NO2(g)
(a) Calculate: The number of moles of NO2 present in equilibrium.
Hints: Remember that concentrations should be in molarity. Also, think about how you might use a variable
(e.g. “x”) to represent “Change” in your ICE.
(b) Calculate the percentage of the original N2O4 that is dissociated.