Chemistry 2720 Fall 1998 Test 2

1. Suppose that you want to make a compound (P) by the reaction

   

   Unfortunately, the equilibrium constant for the reaction is very small. What could you do to get a reasonable yield of the product? [5 marks]

2. State whether each of the following hydrogenic states is possible or impossible. If the state is possible, give the corresponding values of n, and . Otherwise, explain why it is not possible. [6 marks]
   1. 
   2. 
   3. 
3. The emission spectra of H atoms and of ions are similar in appearance, but the lines are found at different wavelengths. The hydrogen spectrum has a blue line at 434nm. Where would the corresponding line in the spectrum of appear? [6 marks]
4. Physicists sometimes speculate about how the Universe would be different if various fundamental constants had different values. Suppose that h were . The radius of a Bohr orbit allows us to approximate the size of a hydrogenic atom. By extension, this gives us an idea of how big atoms are in general. Since all matter is made of atoms, this in turn controls how big everything else is. How much larger or smaller would everything be in the high-h universe? [3 marks]
5. In most organisms which generate their energy from oxidative metabolism, oxygen acts as the oxidizing agent. However, there is no particular reason why some other element or compound cannot serve this role. Suppose that an organism evolved in an oxygen-free, high-sulfur environment such as is found near underwater volcanic vents and that in these organisms, elemental sulfur is the oxidizing agent used in metabolism. Note that sulfur is a solid.
   1. Calculate the maximum work which can be performed per mole of glucose at 298K from the oxidation of aqueous glucose by sulfur. The products are aqueous carbon disulfide and water and the concentrations of glucose and of are, respectively, 0.2 and . The standard free energy of formation of aqueous carbon disulfide is approximately 75kJ/mol. [5 marks]  
   2. Compare your answer to question 5a to the maximum work which can be obtained from the oxidation of aqueous glucose by aqueous oxygen under similar conditions, i.e. 0.2mol/L glucose, and dissolved oxygen. Is there an advantage to using one or the other oxidizing agent? [5 marks]
6. Tetrafluoroethene (the monomer from which teflon is made) is made industrially by a two-step process for which the net reaction is

   

   Suppose that you want to carry out this reaction at 298K in a rigid reactor with initial pressures of and HF of 1 and 15atm, respectively. What are the equilibrium pressures of all reactants and products? [10 marks]

   Hint: A little thought about the size of the equilibrium constant leads to an approximate method of solution which gives a reasonable answer.

7. Estimate the temperature at which water freezes from an aqueous solution containing 0.4mol/L isopropanol. At , the mole density of water is 55.49mol/L and the enthalpy of freezing is -6.007kJ/mol. [10 marks]