CH353 - Physical Chemistry I
Spring 2013, Unique 52575

Homework, Week 10


Homework, week 10
Answer key

1.  Determine DG0rxn and KP at 298 K for each of the following reactions:

                        a)  N2O4(g) « 2 NO2(g)

                        b)  H2(g) + I2(g) « 2 HI(g)

                        c)  3 H2(g) + N2(g) « 2 NH3(g)

2.  The synthesis of ammonia is given by the formula

                        N2(g) + 3 H2(g) « 2 NH3(g)

a) If you begin the reaction with n0 moles of N2(g) and 3n0 moles of H2(g), find an exact expression for zeq.  Use this expression to discuss how zeq varies with P and relate your conclusions to Le Chatelier’s principle. 

3.  Sufuryl chloride, SO2Cl2, decomposes to sulfur dioxide and chlorine gas:

                        SO2Cl2(g) « SO2(g) + Cl2(g)

DG0f (SOCl2) = -371.3 kJ/mol, DG0f (SO2) = -300.2 kJ/mol.

a)  Determine the equilibrium concentrations of each species if the system initially contains 1 mole of SO2Cl2 and 0 moles of SO2 and Cl2 at 1 bar 

b) Determine the equilibrium concentrations of each species if the system initially contains 1 mole of SO2Cl2, 1 mole of SO2, and 0 moles of Cl2 at 1 bar.

c)  Describe any differences according to Le Chatelier’s principle.

4.  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?

5.  Until recently, values of KP were reported assuming a standard state of 1 atm.  Determine a general equation for converting KP values at 1 atm to 1 bar.

6.  Under certain conditions, water vapor dissociates into H2(g) and O2(g).  At 2000 K and 1 bar, water vapor is 0.53% dissociated.  At 2100 K and 1 bar, it is 0.88% dissociated.  Determine the enthalpy of the dissociation reaction, assuming it is constant over this temperature range.