homework_452hmwk3 - 452 Homework Set #3 This homework set...

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©2010 Sarah L. Keller 452 Homework Set #3 This homework set will probably consume more of your paper than Homework #2, but most students find it is easier and takes a little less time. See syllabus for due dates Motto: Sometimes life gives you exactly the information you need… sometimes too little … sometimes too much. The trick is to figure out what you do need. --------------------------------------------------------------------------------------------------------------- 1) (a) As heat is added to pure ice (solid H 2 O) at constant pressure, the temperature rises until the melting point of the ice is reached. This is sketched in the two plots below. The ice then melts at the (constant) melting temperature T m . After the ice is completely melted, the temperature continues to rise. Sketch these two additional stages in the plots below. (b) As heat is added to a dilute buffer solution, the temperature rises. The change in temperature is approximately linear with added heat, as shown in the sketches. If a solution of DNA in dilute buffer is heated, the DNA double-stranded helix separates into single strands over a narrow temperature range. Heat is absorbed. The midpoint of the temperature range is called T m . Sketch what this transition would look like in a plot of q vs. T and of Cp vs. T. In other words, just repeat part a for a system that is a bit messier and will not have as sharp of a transition. This problem taken from Tinoco 2.4. 2) On one fine spring day (T = 20 ˚ C), space alien Zorg shoots you with his blaster. Initially, you are mostly water at 37 ˚ C. The effect of the blaster on your body is first to heat it, and then to vaporize it. You may assume that V gas - V liquid ± V gas and that your vaporized remains behave as an ideal gas at 100 ˚ C. a) How much enthalpy did Zorg’s blaster deliver? b)
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homework_452hmwk3 - 452 Homework Set #3 This homework set...

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