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Problem Set 7

Page history last edited by Paul Cooper 10 years, 4 months ago

1) At 2257 K and 1.00 atm total pressure, water is 1.77 per cent dissociated at equilibrium by way of the reaction 2 H2O(g) <---> 2 H2(g) + O2(g). Calculate (a) K, (b) ΔrG_, and (c) ΔrG at this temperature. 

 

2) Dinitrogen tetroxide is 18.46 per cent dissociated at 25°C and 1.00 bar in the equilibrium N2O4(g) <---> 2 NO2(g). Calculate (a) K at 25°C, (b) ΔrG_, (c) K at 100°C given that ΔrH_ = +57.2 kJ mol–1 over the temperature range.

 

3) From information in the Data section, calculate the standard Gibbs energy and the equilibrium constant at (a) 298 K and (b) 400 K for the reaction PbO(s) + CO(g) <---> Pb(s) + CO2(g). Assume that the reaction enthalpy is independent of temperature. 

 

4) In the gas-phase reaction 2 A + B <---> 3 C + 2 D, it was found that when 1.00 mol A, 2.00 mol B, and 1.00 mol D were mixed and allowed to come to equilibrium at 25°C, the resulting mixture contained 0.90 mol C at a total pressure of 1.00 bar. Calculate (a) the mole fractions of each species at equilibrium, (b) Kx, (c) K, and (d) ΔrG_.  

 

5) The standard reaction Gibbs energy of the isomerization of borneol (C10H17OH) to isoborneol in the gas phase at 503 K is +9.4 kJ mol–1. Calculate the reaction Gibbs energy in a mixture consisting of 0.15 mol of borneol and 0.30 mol of isoborneol when the total pressure is 600 Torr. 

 

6) The standard Gibbs energy of formation of NH3(g) is –16.5 kJ mol–1 at 298 K. What is the reaction Gibbs energy when the partial pressure of the N2, H2, and NH3 (treated as perfect gases) are 3.0 bar, 1.0 bar, and 4.0 bar, respectively? What is the spontaneous direction of the reaction in this case? 

 

 

7) Write the cell reaction and electrode half-reactions and calculate the standard emf of each the following cells: 

 (a) Zn|ZnSO4(aq)|| AgNO3(aq)|Ag

 (b) Cd|CdCl2(aq)|| HNO3(aq)|H2(g)|Pt

 (c) Pt|K3[(CN)6](aq),K4[(CN)6](aq)|| CrCl3(aq)|Cr

 

 

8) Devise cells in which the following are the reactions and calculate the standard emf in each case:

(a) Zn(s) + CuSO4(aq) -> ZnSO4(aq) + Cu(s)

                (b) 2 AgCl(s) + H2(g) -> 2 HCl(aq) + 2 Ag(s)

(c) 2 H2(g) + O2(g) -> 2 H2O(l)

 

 

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