ch20-p017 - 17(a The final mass of ice is(1773 g 227 g/2 =...

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17. (a) The final mass of ice is (1773 g + 227 g)/2 = 1000 g. This means 773 g of water froze. Energy in the form of heat left the system in the amount mL F , where m is the mass of the water that froze and L F is the heat of fusion of water. The process is isothermal, so the change in entropy is Δ S = Q / T = mL F / T = –(0.773 kg)(333 × 10 3 J/kg)/(273 K) = 943 J/K. (b) Now, 773 g of ice is melted. The change in entropy is = = = +943 J/K. F Qm L S TT Δ (c) Yes, they are consistent with the second law of thermodynamics. Over the entire cycle, the change in entropy of the water-ice system is zero even though part of the cycle is irreversible. However, the system is not closed. To consider a closed system, we must
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This note was uploaded on 06/03/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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