1. Announcements If you don’t have a clicker with you, sign in after class If you don’t have a clicker with you, sign in after class Tutoring hours this week: Tutoring hours this week: Monday 12:00-2:00pm Tuesday 10:00am -12:00pm; 2:00-3:00pm; 5:30-8:30 pm Wednesday 2:00-5:00pm and 5:30-8:00pm Quote of the day: The quality of mercy is not strain'd, It droppeth as the gentle rain from heaven Upon the place beneath: it is twice blest; It blesseth him that gives and him that takes:

2. IR Spectroscopy Lab  Infrared radiation promotes molecules to excited vibrational states  IR Spectroscopy Uses  Identify chemical groups  Probe bond strength  Vibration depends on masses and bond strength  Measure, calculate k  Higher k, stronger bond

3. IR Spectroscopy Lab- Conjugation  Conjugation- alternating single and double bonds, lowers energy of molecule because electrons are delocalized  Remember: A pure double bond is stronger than a single bond  Resonance

4. IR Spectroscopy Lab- Ring Strain  Remember molecular structure and “ideal” geometries  C with 4 structural pairs= tetrahedral (109.5°)  Atoms bonded in ring impose geometric constraint  Effect of ring strain and conjugation combined

5. IR Spectroscopy Lab- Metal Carbonyl Bonding  Valence Bond Theory  Atomic orbitals hybridize (sp, sp 2, etc.)  Bonding occurs when hybrid atomic orbitals overlap  Molecular Orbital Theory  Atomic orbitals combine to form molecular orbitals  Bonding- add atomic orbitals  Draws atoms together  To strengthen bond, add e - density to bonding orbital  Antibonding  Draws atoms apart  To weaken bond, add e - density to antibonding orbital

6. IR Spectroscopy Lab- Metal Carbonyl Bonding  Trends in metal binding  Hint: Look at the change in charge- what effect does increasing the charge have on the CO bond?  Final part of lab L-Ni(CO 3 )

7. Chapter 19 Entropy and Free Energy

8. Ammonium nitrate dissolving in water  NH 4 NO 3 (s) → NH 4 + (aq) + NO 3 - (aq) Δ H o = 25.41 kJ/mol  What happens?  What type of reaction is this?  Why on earth would this ever occur?!?

9. Control of Chemical Reactions

10. Thermodynamic Control of Reactions Enthalpy  Bond Energies  Forming stronger bonds favors reactions.  Molecules with strong bonds are more stable. Entropy  Randomness  Reactions that increase randomness are favored.  Forming gases favors reactions. QuantityQuality

11. The Laws of ThermodynamicsThe Laws of Thermodynamics  1st Law: Energy is Conserved  2 nd Law: Any spontaneous process leads to an increase in entropy of the universe.  What do we mean by “spontaneous”?

12. Spontaneous reactions

13. Which of the following has the least entropy? 1.H 2 O( s ) 2.H 2 O( l ) 3.H 2 O( g ) 4.a and b have the same entropy 5.a, b, and c have the same entropy

14. Entropy A measure of randomness. Units of J/K.