Chapter 2 Flashcards
How many hydrogen bonds does liquid H2O have?
3.4
How many hydrogen bonds does ice have?
4.0
How fast do hydrogen bonds break and reform?
pico second (10^-12)
What kind of interaction is a hydrogen bond?
Intermolecular (electrostatic) interaction
Hydrogen bonds mostly occur between what atoms?
H, O, N, F
Explain why ice floats on water
Ice forms crystal lattice and has 4 fixed hydrogen bonds that are maximally spread apart (less molecules per area, which causes a decreased density) Water constantly makes and breaks hydrogen bonds and averages 3.4 bonds at any moment, but the molecules are able to be positioned much closer together (more molecules per area, which causes increased density)
Orientation of hydrogen bonds in liquid water
Straight
Orientation of hydrogen bonds in ice
Bent
Why is it a bad idea to use NaCl on the sidewalks as a deicer when you run out of CaCl2?
NaCl completely ionizes in water because it is a polar molecule (Na+ and Cl-) salt that forms two ions. CaCl2 ionizes into three molecules and the solute interferes with the hydrogen bond formation (makes the hydrogen bonds weaker).
*Colligative properties
What is entropy?
The measure of randomness in a system (deltaS)
Example of increased entropy
Boiling
Example of decreased entropy
Freezing
What orientation of fatty acid formation is favorable in an aqueous solution and why?
Micelle is favored because less nonpolar surface area is interacting with water molecules. Less ordered water is needed to surround the molecule, and allows for an larger entropy (deltaS) overall in the system.
Explain how the hydrophobic effect can drive enzymatic reactions in the forward direction.
Hydrophobic effect increases entropy of a system by requiring less ordered water to surround the enzyme and the substrate in aqueous solution if they are both complexed together. This makes the reaction favorable and drives it in the forward direction.
Define amphiphillic
Has hydrophobic and hydrophillic ends
