The second law The Concepts Chemistry 331
Chemistry 331 The Second Law The Concepts
The Laws of Thermodynamics First law You cant get something for nothing Second law You can t even break even Chemistry 331
Chemistry 331 The Laws of Thermodynamics • First Law You can’t get something for nothing. • Second Law You can’t even break even
Heat engines a heat engine converts heat into work Th=temperature ofheat source Engine c=temperature of heat sink gh= heat supplied 」qn qe heat released W=work produced Chemistry 331
Chemistry 331 Heat Engines • A heat engine converts heat into work. • Th = temperature of heat source • Tc = temperature of heat sink • qh = heat supplied • qc = heat released • w = work produced Th Tc Engine qh qc w
efficiency of heat engines An engine operates in You can iget a cycle:. AU=O something for and w=gh-lqcl nothing. efficiency is given b 8=w /qr q cl / gh q>o implies a< 1 You can t even breakeven Chemistry 331
Chemistry 331 Efficiency of Heat Engines • An engine operates in a cycle; \ DU = 0 and |w| = qh - |qc | • efficiency is given by e = |w| / qh \ e = 1 - |qc | / qh • |qc |>0 implies e < 1 You can’t get something for nothing. You can’t even break even
The Second law(Kelvin) No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work In other words, w<gh and the efficiency of a heat engine is less than 100% Chemistry 331
Chemistry 331 The Second Law (Kelvin) • No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. • In other words, |w| < qh and the efficiency of a heat engine is less than 100%