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Chemistry 2720, Fall 1996, Test 1

  1. Calculate tex2html_wrap_inline132 and tex2html_wrap_inline134 for the combustion of ethanol forming liquid water at 298K. [5 marks]
    1. An Inuit hunter is out on a day in early Spring when the air temperature is tex2html_wrap_inline136 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 ( tex2html_wrap_inline138 ). 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 tex2html_wrap_inline140 . 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]
    1. Use an entropy calculation to show that ice will melt in a room at tex2html_wrap_inline142 . [5 marks]
    2. Use a free energy calculation to show that ice will melt in a room at tex2html_wrap_inline142 . Hint: Assume that tex2html_wrap_inline146 and tex2html_wrap_inline148 depend only weakly on temperature. [5 marks]
  2. 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

    displaymath150

    For this reaction, tex2html_wrap_inline152 and tex2html_wrap_inline154 at 298K. Suppose that the concentration of G6P in an organelle at tex2html_wrap_inline138 is tex2html_wrap_inline158 , the concentration of glucose is tex2html_wrap_inline160 and the total concentration of phosphates is tex2html_wrap_inline162 . What is the maximum work available from this reaction per mole of G6P? [10 marks]

  3. 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 tex2html_wrap_inline164 C and the plant's freezer is held at tex2html_wrap_inline166 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 tex2html_wrap_inline168 C. What is the minimum electrical work (per day) required to bring the turkeys to their final temperature of tex2html_wrap_inline136 ? [15 marks]


Next: Useful formulas Up: Back to the old Chemistry 2720 index

Marc Roussel
Tue Oct 15 14:51:57 MDT 1996