Chemistry 2720, Fall 1996, Test 1

1. Calculate and for the combustion of ethanol forming liquid water at 298K. [5 marks]
2. 1. An Inuit hunter is out on a day in early Spring when the air temperature is and the atmospheric pressure is 100kPa. Due to the intense physical activity of hunting, the hunter's average breathing rate over a six hour period is 15 breaths per minute and each breath has a volume of 0.6L at body temperature ( ). The air inspired is warmed to body temperature on the way to the lungs. How much heat is lost in the process of breathing during this six hour period? The specific heat capacity of air at constant pressure is approximately . Note that air may be treated as an ideal gas. [5 marks]
   2. Seal blubber is almost pure fat. How much seal blubber does the hunter have to eat to offset the energy loss from breathing during the six hours of hunting? The catabolizable energy available from fat is 9.5kcal/g. [5 marks]
3. 1. Use an entropy calculation to show that ice will melt in a room at . [5 marks]
   2. Use a free energy calculation to show that ice will melt in a room at . Hint: Assume that and depend only weakly on temperature. [5 marks]
4. While ATP is the principal short-term energy storage compound in living organisms, many other compounds are used for this purpose. Glucose-6-phosphate (G6P) is an intermediate in glucose metabolism but it can be and sometimes is used as a source of work. Its hydrolysis reaction is

   

   For this reaction, and at 298K. Suppose that the concentration of G6P in an organelle at is , the concentration of glucose is and the total concentration of phosphates is . What is the maximum work available from this reaction per mole of G6P? [10 marks]

5. Most of the foods we eat are mostly water. Thus, refrigerating or freezing them is approximately equivalent to refrigerating or freezing an equal mass of water. Suppose that a packing plant freezes 20000kg of turkey per day. These turkeys are initially at C and the plant's freezer is held at C. (The turkeys are taken into the freezer continuously over the course of the day so that its temperature is essentially constant.) The freezer's coils are on the roof of the building and it's a nice warm September day, with an exterior temperature of C. What is the minimum electrical work (per day) required to bring the turkeys to their final temperature of ? [15 marks]