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AP Chem Rules!
100

What is the equilibrium expression for this reaction? P4(s) + 5 O2(g) ↔ P4O10(s)

Kc = [P4O10] / [P4] [O2] 5

100

Xenon tetrafluoride, XeF4, can be prepared by heating Xe and F2 together according to this equation. What is the equilibrium expression for this reaction? 

Xe(g) + 2F2(g) ↔ XeF4(g)

K = [XeF4] / ( [Xe] [F2] 2 )

200

N2(g) + 3 H2(g) --> 2 NH3(g) 

At equilibrium: [N2] = 1.50 M [H2] = 2.00 M [NH3]= 0.01 M

Calculate the value of Kc and state whether each equilibrium is product-favored, reactant-favored, or fairly even.

Kc = 8.33 x 10-6 and it is reactants-favored

200

Write the equilibrium expression for the following reaction: Ni(s) + 4CO(g) --> Ni(CO)4(g)

Kp = (PNi(CO)4) / (PCO)4

300

Write the Kc expression for 2 SO2(g) + O2(g) --> 2 SO3(g) Calculate the value of Kc: 4.36 At equilibrium: [SO2] = 1.50 M [O2] = 1.25 M [SO3]= 3.50 M

Kc = [SO3]2 / [SO2]2 [O2] and 4.36

300

2C(g) <--> A(g) + B(g)      Kp = 0.00034

When 50 atm of C(g) is added to an empty, rigid container and allowed to reach equilibrium, the partial pressure of A(g) is approximately 5.6 atm. If the initial pressure of C(g) is decreased to 25 atm and the process is repeated at the same temperature, what is the correct prediction for the equilibrium partial pressure of A(g) and why?

PA ~ 2.8 atm because it is directly proportional to the pressure of C(g)

400

The particle diagram above shows the changes that take place between two particles when placed in a rigid container at a constant temperature. Describe if/when the system reached equilibrium and how did you know.

It reached equilibrium between t=2 and t=3 because the amounts of each species remained constant after that point.

400

Consider an equilibrium that occurs in two steps: H2S(aq) --> H+ (aq) + HS- (aq)

HS- (aq) --> H+ (aq) + S2- (aq)

a) Write the overall reaction.

b) How do the Kc’s for the two steps (Kc1 & Kc2) relate to the Kc of the overall reaction (Kc)?

H2S(aq) --> 2H+(aq) + S2-(aq)

Kc = Kc1 x Kc2

500

Calculate the value of Kc for the reaction:  2 N2O(g) + 3 O2(g)  2 N2O4(g), using the following information.

1.1 x 106

500

Write the equilibrium expression for the equation below and determine the pressure of CO if at equilibrium (PO2) = 1.6 x 10-3 atm, (PCO2) = 3.2 x 10-2 atm,  and Kp = 1.02 x 105

2 CO(g) + O2(g) ↔ 2CO2(g)

(PCO) = 2.5 x 10-3 atm