From: del@branta.demon.co.uk   
      
   On Fri, 28 Jan 2005, in sci.space.tech,   
   iain-3@truecircuits.com said:   
      
   >The JANAF heat of formation for C is 711.2 kJ/mol.  That's a lot.   
   >   
   >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)   
   >   
   >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)   
   >   
   >That's a lot better!   
   >   
   >I haven't heard of this before, so I'm probably screwing up.   
   >Can anyone suggest where I'm screwing up?   
      
   Have you taken the entropy of formation into account?  Carbon monoxide   
   has a large positive entropy of formation.  Carbon is unusual among   
   oxides, since most solid elements form solid oxides, not gaseous ones,   
   and thus have negative entropy of formation.  But carbon dioxide makes   
   as many moles of gas as the oxygen it was formed from, giving it an   
   entropy close to zero, and carbon monoxide makes *two* moles of gas for   
   every mole of oxygen gas.   
      
   --   
   Del Cotter   
   Thanks to the recent increase in UBE, I will soon be ignoring email   
   sent to del@branta.demon.co.uk.  Please send your email to del2 instead.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)