Name: _________________________________________
Date:____________________________
Required Homework 4
1.) If the equilibrium concentrations of Cl2 and COCl2 are found to be the same at 395oC, find the
equilibrium concentration of CO in the reaction that follows:
CO(g) + Cl2  COCl2 (g)
Kc = 2.8 x 104
2.) Given Kc = 2.9 x 10-8 for the reaction of 2NO(g) + O2 (g)  2NO2 (g) at 457 K
derive the Kp value for the following reaction NO2 (g)  NO (g) + ½ O2 (g)
3.) Consider the equilibrium between gaseous dinitrogen tetraoxide (written as the reactant) and
gaseous nitrogen dioxide (written as the product). Write and balance the chemical reaction. If the
Kp for the reaction at 319 K is 0.750 answer the following questions:
Rxn: ______________________________________________________________________
a. In the equation above, if the equilibrium partial pressure of nitrogen dioxide gas is found to
be 0.221 atm (PNO2 = 0.221 atm) , what is the equilibrium partial pressure for dinitrogen
tetraoxide?
b. What is the numerical value of Kp if the reaction is reversed?
4.) Chloromethane forms by the reaction:
CH4 (g) + Cl2 (g)  CH3Cl (g) + HCl (g)
If the Kp value = 1.6 x 104 and the pressures of each species are:
PCH4 = 0.13 atm PCl2 = 0.035 atm PCH3Cl = 0.24 atm and PHCl = 0.47 atm
Calculate Qp
Is the reaction at equilibrium?
Yes
No
Briefly explain how you made that choice:
If the system is not at equilibrium, which direction does it need to go in order to reach equilibrium?
Left
right
Why does it need to proceed in the direction you circled above?
5.) Consider the following reaction:
H2 (g) + I2 (g)  2HI (g)
The initial concentrations of H2, I2 are 0.02000 M, 0.03000 M. If the equilibrium concentration of H2 is
0.00188 M, determine K
6.) Consider the following reaction: Xe (g) + F2 (g) --> XeF2 (g) and assume the equilibrium constant is
K = 1.2 x 103 . Let’s examine what happens when the total amount of material is kept constant, but
starts with different proportions in reactant and product form. For this exercise, keep 5 digits for
comparison purposes.
a) If the starting concentrations in the reaction vessel are
[Xe] = [F2] = 0.15M and [XeF2] = 0.17M, determine the equilibrium concentrations.
b) Calculate the equilibrium concentrations if the starting concentrations are [Xe] = [F2] = .32M and
[XeF2] = 0M
c) Repeat for [Xe] = [F2] = 0M and [XeF2] = 0.32M
How do the equilibrium concentrations depend on how much material began in reactant form and
how much in product form?
DO NOT DO FOR HOMEWORK**: FOR EXAMPLE ONLY: And another problem type to
consider: examine the following reaction:
H2 (g) + I2 (g)  2HI (g)
The concentrations of H2, I2, and HI are 0.0200 M, 0.0200 M, and 0.0400 M respectively
The Kc for this reaction is 50.3 at 458oC.
**NOTE – you should look at the answer key for this problem before the exam!