Lecture_22 - 5. Entropy changes in chemical reactions: 2nd...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 5. Entropy changes in chemical reactions: 2 nd Law: for a spontaneous process: S univ. > 0 G sys. < 0 We applied those forms to physical processes such as changes of state and formation of solutions. Entropy changes in the system are determined by the Positional Probability. examples : N 2 (g) + 3 H 2 (g) 2 NH 3 (g) fewer molecules fewer possible configurations S Rxn. ≡∆ S sys. < 0 4 NH 3 (g) + 5 SO 2 (g) 4 NO (g) + 6 H 2 O (g) + 5 S (s) 9 gas molecules 10 molecules S sys. > 0 In a reaction involving gaseous molecules, the change in the positional entropy is dominated by the relative numbers of molecules of gaseous reactants and products. S sys. > 0 •CaCO 3 (s) CaO (s) + CO 2 (g) •O 2 (g) + 2 SO 2 (g) 2 SO 3 (g) S sys. < 0 In θ ics, we can measure E , H , G …We cannot determine absolute internal energy, enthalpy or free energy. BUT, we can assign absolute entropies!!
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 −+ + Consider an HCl crystal at 0°K: Perfect Arrangement S = 0 Increase T Random vibrational motion increases.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

Lecture_22 - 5. Entropy changes in chemical reactions: 2nd...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online