From: henry@spsystems.net   
      
   In article <1106946940.727340.289100@c13g2000cwb.googlegroups.com>,   
     wrote:   
   >The JANAF heat of formation for C is 711.2 kJ/mol.  That's a lot.   
      
   Uh, the heat of formation for an element in its room-temperature   
   state is *zero* by definition.   
      
   You're looking at the heat of formation for carbon *gas*.  And it's   
   positive -- you have to put a bunch of energy *in* to get the gas,   
   starting from the solid.  Which is not a surprise...   
      
   >If I do the simple heat of formation at 0 K equation for a   
   >hydrogen-oxygen rocket, I get:   
   >H2 + 0.5*O2 -> H20 + 238.9 kJ/mol  (= 13.27 kJ/g)   
      
   Correct.   
      
   >If I do the same equation for a carbon monoxide rocket, I get:   
   >C + 0.5*O2 -> CO + 825.0 kJ/mol    (= 29.45 kJ/g)   
      
   No, sorry, you get about 111 kJ/mol, about 4 kJ/g.  It's just the heat of   
   formation of CO.  The two reactants are both elements in their normal   
   states, so their heats of formation are zero.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
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