Chemistry 2720 Fall 1995 midterm examination

All questions are weighted equally.

Note the structure of this test: We start with some instructions or information. Then follow the questions. Finally, a data section is appended. (These are often printed on the reverse side of the test. In the on-line version, there is a button which takes you there.)

1. Maple sugar is made by evaporating water from sap. Sugar maple sap is approximately 98% water by weight.
   1. How much sap does it take to make 100g of maple sugar?
   2. If the sap is heated by burning decane (enthalpy of combustion: -34.56MJ/L), how much fuel must be burned to make 100g of maple sugar from sap at C (a typical harvest temperature)?
2. After discovering oxygen and its involvement in combustion, Lavoisier proposed that living organisms literally burn their foods.
   1. Very few cells can survive temperatures in excess of C. Suppose that cells converted heat to work directly in some organelles which maintained themselves at this temperature, but were surrounded by cytoplasm at C. What is the maximum amount of work which could be obtained in this manner per mole of glucose burned? (Assume that the combustion produces liquid water rather than steam as its end product.)
   2. Why is this not a very smart way for cells to produce work? What is the maximum work which can be obtained under standard conditions from the oxidation of glucose using a better strategy?
3. Glucose is actively transported by many cells. If this process is powered by ATP hydrolysis

   

   ( kJ/mol at 310K) how large a ratio of glucose concentrations can the cell maintain across its outer membrane? Take the ratio of ATP to ADP in the cell to be 20 and the activity of phosphate to be . Assume that one glucose molecule is transported for every ATP hydrolyzed.

4. 1. What is the vapour pressure of hydrogen peroxide at 298K?
   2. Predict the normal boiling point of hydrogen peroxide.
5. What are the enthalpy and free energy of formation of steam at 500K?