CH302H - Principles of Chemistry II: Honors
Spring 2016, Unique 494200

Homework, Week 4

Homework, week 4
Answer key

1. The water-gas shift reaction is an important industrial source of pure H2(g) for ammonia synthesis:

CO(g) + H2O(g) --> H2(g) + CO2(g)

What would happen to the equilibrium concentration of each species if you increase the total pressure of the system by a factor of 100?

2.  Under certain conditions, water vapor dissociates into H2(g) and O2(g). At 2100 K and 1 bar, the equilibrium constant for the dissociation reaction is twice as large as at 2000 K and 1 bar.   Determine the enthalpy of the dissociation reaction, assuming it is constant over this temperature range.

3.  Dimethyl ether can be made from the dimerization of methanol:

2 CH3OH(g) --> (CH3)2O(g) + H2O(g)

Describe, both quantitatively and qualitatively, the optimum conditions of pressure and temperature to make as much of this chemical as possible.

4.  A flask is filled with 1.32 atm of H2(g) and 1.14 atm of I2(g), sealed, and heated to 600 K, where they react to form HI(g).

a) Write the stoichiometrically balanced reaction.

b) Write the equilibrium constant expression for the reaction in part a).

c) How much H2(g), I2(g), and HI(g) are present at equilibrium?

d) What fraction of the I2(g) originally introduced to the flask has reacted when equilibrium is reached?

5.  Write the equilibrium expressions for the following reactions.

a) 8 H2(g) + S8(s) --> 8H2S(g)


b) C(s) + H2O(l) + Cl2(g) --> COCl2(g) + H2(g)


c) CaCO3(s) --> CaO(s) + CO2(g)


d) 3 C2H2(g) --> C6H6(l)

6.  Given the following two reactions, with equilibrium constants K1 and K2:

Reaction 1: XeF6(g) + H2O(g) --> XeOF4(g) + 2 HF(g)

Reaction 2: XeO4(g) + XeF6(g) --> XeOF4(g) +  XeO3F2(g)

Determine the equilibrium constant for the following reaction:

XeO4(g) + 2 HF(g) --> XeO3F2(g) + H2O(g)

In terms of K1 and K2.