HW Key _11 s problems part b

# HW Key _11 s problems part b - S40 Using the thermodynamic...

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S40. Using the thermodynamic data from your textbook, calculate Δ S° at 298K for each of the following reactions. Explain the sign of each of the entropy changes by qualitatively comparing the molecular disorder in the reactants and products. To find Δ S°, we need to take the product of the number of moles and the standard molar entropies and sum up those results for both the reactants and the product, then take the difference of the two sums according to the equation Δ S ° = nS m ° (products) nS m ° (reactants) a) Cl 2 (g) 2Cl(g) Δ S ° = (2 moles) × (165.2 J/mole K) (1 mole) × (223.07 J/mole K) =107.33 J/K The sign is positive because chlorine atoms are more randomly distributed (they have a larger number of microstates and hence greater disorder) than the paired atoms or Cl 2 . Therefore going from Cl 2 to 2 Cl increases the entropy of the system. b) H 2 O(l) H 2 O(g) Δ S ° = (1 mole) × (188.83 J/mole K) (1 mole) × (69.91 J/mole K) =118.92 J/K

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HW Key _11 s problems part b - S40 Using the thermodynamic...

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