1. Life’s Water: Necessary and Abundant
Human H2O content:
Life on Europa (Jupiter moon) only considered if H2O is present
Even in unusually cold hearty Antarctic bacteria (e.g. -2C) H2O is essential

2. Water Unlike its Molecular Neighbors
Compound MW BP MP
H2S Sulfide
H2Se Selenide
H2Te Telluride
H2O Water
As the molecule becomes heavier how should this affect boiling point and melting point?

3. Unusual Physical Properties of H2O
Adhesion – sticks to other molecules
Cohesion – sticks to itself
High surface tension

4. Water Hydrogen Bonding: Weak But Abundant
Distance for:
Covalent
H-bonding
Non-interacting
Where is H-bonding on this graph?
Van der
Waals radius
Van der Waals Radius: distance from nucleus to effective electron surface

5. Hydrogen Bonding in Water
Oxygen Electronic configuration?
Bond angle?

6. DNA Base Pair Hydrogen Bonding

7. Relative Bond Strengths
400
Where do dipole-dipole interactions fit into this ranking?
100 20
0.1

8. Hydrogen-Bonding Requirement
Differential electronegativity
Name the following interactions:
S – H S

9. Water: the Universal Solvent
Polar solvents weaken
electrostatic interactions

10. Dielectric Solvent Constants1
1Dielectric solvent constant is a measure of the ability of a solvent to diminish electrostatic attraction between dissolved ions

11. Hydrophobic Effect ∆G = ∆H - TΔS
Exclusion of non-polar substances from a water phase
Entropy driven
∆G = ∆H - TΔS

12. Single Tail Amphipathic Molecules: Micelles
What is the driving force for this reaction?

13. Double Tail Amphipathic Molecules: Bilayer

14. A Bilayer Limits Movement of Polar Substances

15. Driving Force for Protein Folding: Hydrophobic Effect
Amphipathic molecules contain
both hydrophobic and hydrophilic
portions

16. pH Versus pKA
Is a molecule
always charged or uncharged?

17. Ka/pKa Values

18. Le Chatelier’s Principle
When a system in a state of dynamic equilibrium is acted upon by some outside stress, the system will, if possible, shift to a new position of equilibrium in order to minimize the effect of the stress.

19. Acetic Acid Titration Curve
What is the effective buffering range?

20. pKA = -log KA and pH = -log [H+] log KA + log [HA]/[A-] = log [H+]
Henderson-Hasselbalch Equation
pH = pKA – log [HA]/[A-]
pKA = -log KA and pH = -log [H+]
Conceptionally: pKA is the pH at which the ionized and unionized forms are equal. HA ↔ H+ + A-
KA = [A-][H+]/[HA]
KA[HA]/[A-] = [H+]
log KA + log [HA]/[A-] = log [H+]
pH = pKA – log [HA]/[A-]

21. Inverse Relationship: [H+] and [OH-]
pH Value of Biological Fluids
H2O ↔ H+ + OH-
K = [H+][OH-]/[H2O]
KW = K[H2O] = [H+][OH-]
KW = = [H+][OH-]

22. Water Acidification
CO2 + H2O ↔ HCO3- + H+

23. Acids to Buffer at Any pH

24. Chapter 2 Problems:
1-15, 21, 33, 35, 41, 53, 55 and 60